The Commission on Higher Education in collaboration with the Philippine Normal University
INITIAL RELEASE: 13 JUNE 2016
Teaching Guide for Senior High School
GENERAL BIOLOGY 1
SPECIALIZED SUBJECT | ACADEMIC - STEM This Teaching Guide was collaboratively developed and reviewed by educators from public and private schools, colleges, and universities. We encourage teachers and other education stakeholders to email their feedback, comments, and recommendations to the Commission on Higher Education, K to 12 Transition Program Management Unit Senior High School Support Team at
[email protected]. We value your feedback and recommendations.
Development Team Team Leader: Florencia G. Claveria, Ph.D.,
Dawn T. Crisologo Writers: Doreen D. Domingo, Ph.D., Janet S. Estacion, Ph.D., Mary Jane C. Flores, Ph.D.,
Aileen C. dela Cruz, Chuckie Fer Calsado,
Nolasco H. Sablan, Justin Ray M. Guce
Published by the Commission on Higher Education, 2016
Chairperson: Patricia B. Licuanan, Ph.D. Commission on Higher Education
K to 12 Transition Program Management Unit
Office Address: 4th Floor, Commission on Higher Education, C.P. Garcia Ave., Diliman, Quezon City
Telefax: (02) 441-0927 / E-mail Address:
[email protected]
Consultants THIS PROJECT WAS DEVELOPED WITH THE PHILIPPINE NORMAL UNIVERSITY.
University President: Ester B. Ogena, Ph.D.
VP for Academics: Ma. Antoinette C. Montealegre, Ph.D.
VP for University Relations & Advancement: Rosemarievic V. Diaz, Ph.D. Ma. Cynthia Rose B. Bautista, Ph.D., CHED
Bienvenido F. Nebres, S.J., Ph.D., Ateneo de Manila University
Carmela C. Oracion, Ph.D., Ateneo de Manila University
Minella C. Alarcon, Ph.D., CHED Gareth Price, Sheffield Hallam University
Stuart Bevins, Ph.D., Sheffield Hallam University
Technical Editor: John Donnie A. Ramos, Ph.D. Copy Reader: Joy R. Jimena Illustrators: Renan U. Ortiz, Daniela Louise B. Go Cover Artists: Paolo Kurtis N. Tan, Renan U. Ortiz
Senior High School Support Team
CHED K to 12 Transition Program Management Unit Program Director: Karol Mark R. Yee Lead for Senior High School Support:
Gerson M. Abesamis Course Development Officers:
John Carlo P. Fernando, Danie Son D. Gonzalvo Lead for Policy Advocacy and Communications:
Averill M. Pizarro Teacher Training Officers:
Ma. Theresa C. Carlos, Mylene E. Dones Monitoring and Evaluation Officer:
Robert Adrian N. Daulat Administrative Officers:
Ma. Leana Paula B. Bato, Kevin Ross D. Nera, Allison A. Danao, Ayhen Loisse B. Dalena Printed in the Philippines by EC-TEC Commercial, No. 32 St. Louis Compound 7, Baesa, Quezon City,
[email protected]
This Teaching Guide by the Commission on Higher Education is licensed under a Creative Commons Attribution-NonCommercialShareAlike 4.0 International License. This means you are free to: Share — copy and redistribute the material in any medium or format Adapt — remix, transform, and build upon the material. The licensor, CHED, cannot revoke these freedoms as long as you follow the license terms. However, under the following terms: Attribution — You must give appropriate credit, provide a link to the license, and indicate if changes were made. You may do so in any reasonable manner, but not in any way that suggests the licensor endorses you or your use. NonCommercial — You may not use the material for commercial purposes. ShareAlike — If you remix, transform, or build upon the material, you must distribute your contributions under the same license as the original.
Table of Contents Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1
DepEd General Biology 1 Curriculum Guide . . . . . . . . . . . . .
5
Chapter 3: Energy Transformation
Chapter 1: Cell
Lesson 11: Photosynthesis and Cellular Respiration . . . . . . . . . . .
86
Lesson 1: The Cell: Endomembrane System, Mitochondria,
99
Chloroplasts, Cytoskeleton, and Extracellular Components . . .
9
Lesson 12: Forms of Energy, Laws of Energy Transformation and Role of ATP . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Lesson 2: Mitochondria and Chloroplasts . . . . . . . . . . . . . . . . .
15
Lesson 13: Energy Transformation Part 1 . . . . . . . . . . . . . . . . . . . . 111 Lesson 14: Energy Transformation Part 2 . . . . . . . . . . . . . . . . . . . . 120
Lesson 3: Structure and Functions of Animal Tissues and Cell Modification . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
28
Lesson 15: Energy Transformation Part 3 . . . . . . . . . . . . . . . . . . . . 128
Lesson 4: Cell Cycle and Cell Division . . . . . . . . . . . . . . . . . . . . 36
Lesson 16: Cellular Respiration Part 1 . . . . . . . . . . . . . . . . . . . . . .
133
Lesson 5: Transport Mechanisms Part 1 . . . . . . . . . . . . . . . . . . . 46
Lesson 17: Cellular Respiration Part 2 . . . . . . . . . . . . . . . . . . . . . .
150
Lesson 6: Transport Mechanisms Part 2 . . . . . . . . . . . . . . . . . . . 50
Lesson 18: Cellular Respiration Part 3 . . . . . . . . . . . . . . . . . . . . . .
165
Chapter 2: Biological Molecules
Lesson 19: ATP in Cellular Metabolism and Photosynthesis . . . . .
176
Lesson 7: Carbohydrates and Lipids . . . . . . . . . . . . . . . . . . . . .
57
Lesson 8: Amino Acids and Proteins Part 1 . . . . . . . . . . . . . . . .
70
Lesson 9: Amino Acids and Proteins Part 2 . . . . . . . . . . . . . . . .
73
Lesson 10: Biological Molecules: Enzymes . . . . . . . . . . . . . . . .
78
Biographical Notes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 184
Introduction As the Commission supports DepEd’s implementation of Senior High School (SHS), it upholds the vision and mission of the K to 12 program, stated in Section 2 of Republic Act 10533, or the Enhanced Basic Education Act of 2013, that “every graduate of basic education be an empowered individual, through a program rooted on...the competence to engage in work and be productive, the ability to coexist in fruitful harmony with local and global communities, the capability to engage in creative and critical thinking, and the capacity and willingness to transform others and oneself.” To accomplish this, the Commission partnered with the Philippine Normal University (PNU), the National Center for Teacher Education, to develop Teaching Guides for Courses of SHS. Together with PNU, this Teaching Guide was studied and reviewed by education and pedagogy experts, and was enhanced with appropriate methodologies and strategies. Furthermore, the Commission believes that teachers are the most important partners in attaining this goal. Incorporated in this Teaching Guide is a framework that will guide them in creating lessons and assessment tools, support them in facilitating activities and questions, and assist them towards deeper content areas and competencies. Thus, the introduction of the SHS for SHS Framework.
SHS for SHS Framework
The SHS for SHS Framework, which stands for “Saysay-Husay-Sarili for Senior High School,” is at the core of this book. The lessons, which combine high-quality content with flexible elements to accommodate diversity of teachers and environments, promote these three fundamental concepts:
SAYSAY: MEANING
HUSAY: MASTERY
SARILI: OWNERSHIP
Why is this important?
How will I deeply understand this?
What can I do with this?
Through this Teaching Guide, teachers will be able to facilitate an understanding of the value of the lessons, for each learner to fully engage in the content on both the cognitive and affective levels.
Given that developing mastery goes beyond memorization, teachers should also aim for deep understanding of the subject matter where they lead learners to analyze and synthesize knowledge.
When teachers empower learners to take ownership of their learning, they develop independence and selfdirection, learning about both the subject matter and themselves.
About this
Teaching Guide
Biology I is a Science, Technology, Engineering and Mathematics (STEM) Specialized Subject taken in the first half of Grades 11/12. Learners go on a journey geared toward the deeper understanding and appreciation of life processes at the cellular and molecular levels previously introduced in Grades 7-10. They will also apply basic chemistry and physics principles as they examine the transformation of energy in organisms. Implementing this course at the senior high school level is subject to numerous challenges with mastery of content among educators tapped to facilitate learning and a lack of resources to deliver the necessary content and develop skills and attitudes in the learners, being foremost among these. In support of the SHS for SHS framework developed by CHED, these teaching guides were crafted and refined by biologists and biology educators in partnership with educators from focus groups all over the Philippines to provide opportunities to develop the following: Saysay through meaningful, updated, and context-specific content that highlights important points and common misconceptions so that learners can connect to their real-world experiences and future careers; Husay through diverse learning experiences that can be implemented in a resource-poor classroom or makeshift laboratory that tap cognitive, affective, and psychomotor domains are accompanied by field-tested teaching tips that aid in facilitating discovery and development of higher-order thinking skills; and Sarili through flexible and relevant content and performance standards allow learners the freedom to innovate, make their own decisions, and initiate activities to fully develop their academic and personal potential. These ready-to-use guides are helpful to educators new to either the content or biologists new to the experience of teaching Senior High School due to their enriched content presented as lesson plans or guides. Veteran educators may also add ideas from these guides to their repertoire. The Biology Team hopes that this resource may aid in easing the transition of the different stakeholders into the new curriculum as we move towards the constant improvement of Philippine education.
Parts of the
Teaching Guide
This Teaching Guide is mapped and aligned to the DepEd SHS Curriculum, designed to be highly usable for teachers. It contains classroom activities and pedagogical notes, and is integrated with innovative pedagogies. All of these elements are presented in the following parts: 1. • • • • • 2. • • • • 3. • • • • 4. • • • • 5. • • • • 6. • •
Introduction Highlight key concepts and identify the essential questions Show the big picture Connect and/or review prerequisite knowledge Clearly communicate learning competencies and objectives Motivate through applications and connections to real-life Motivation Give local examples and applications Engage in a game or movement activity Provide a hands-on/laboratory activity Connect to a real-life problem Instruction/Delivery Give a demonstration/lecture/simulation/hands-on activity Show step-by-step solutions to sample problems Give applications of the theory Connect to a real-life problem if applicable Practice Discuss worked-out examples Provide easy-medium-hard questions Give time for hands-on unguided classroom work and discovery Use formative assessment to give feedback Enrichment Provide additional examples and applications Introduce extensions or generalisations of concepts Engage in reflection questions Encourage analysis through higher order thinking prompts Evaluation Supply a diverse question bank for written work and exercises Provide alternative formats for student work: written homework, journal, portfolio, group/individual projects, student-directed research project
On DepEd Functional Skills and CHED College Readiness Standards As Higher Education Institutions (HEIs) welcome the graduates of the Senior High School program, it is of paramount importance to align Functional Skills set by DepEd with the College Readiness Standards stated by CHED. The DepEd articulated a set of 21st century skills that should be embedded in the SHS curriculum across various subjects and tracks. These skills are desired outcomes that K to 12 graduates should possess in order to proceed to either higher education, employment, entrepreneurship, or middle-level skills development.
On the other hand, the Commission declared the College Readiness Standards that consist of the combination of knowledge, skills, and reflective thinking necessary to participate and succeed without remediation - in entry-level undergraduate courses in college. The alignment of both standards, shown below, is also presented in this Teaching Guide - prepares Senior High School graduates to the revised college curriculum which will initially be implemented by AY 2018-2019.
College Readiness Standards Foundational Skills
DepEd Functional Skills
Produce all forms of texts (written, oral, visual, digital) based on: 1. 2. 3. 4. 5.
Solid grounding on Philippine experience and culture; An understanding of the self, community, and nation; Visual and information literacies, media literacy, critical thinking Application of critical and creative thinking and doing processes; and problem solving skills, creativity, initiative and self-direction Competency in formulating ideas/arguments logically, scientifically, and creatively; and Clear appreciation of one’s responsibility as a citizen of a multicultural Philippines and a diverse world;
Systematically apply knowledge, understanding, theory, and skills for the development of the self, local, and global communities using prior learning, inquiry, and experimentation
Global awareness, scientific and economic literacy, curiosity, critical thinking and problem solving skills, risk taking, flexibility and adaptability, initiative and self-direction
Work comfortably with relevant technologies and develop adaptations and innovations for significant use in local and global communities
Global awareness, media literacy, technological literacy, creativity, flexibility and adaptability, productivity and accountability
Communicate with local and global communities with proficiency, orally, in writing, and through new technologies of communication
Global awareness, multicultural literacy, collaboration and interpersonal skills, social and cross-cultural skills, leadership and responsibility
Interact meaningfully in a social setting and contribute to the fulfilment of individual and shared goals, respecting the fundamental humanity of all persons and the diversity of groups and communities
Media literacy, multicultural literacy, global awareness, collaboration and interpersonal skills, social and cross-cultural skills, leadership and responsibility, ethical, moral, and spiritual values
General Biology 1
60 MINS
The Cell: Endomembrane System, Mitochondria,
Chloroplasts, Cytoskeleton, and Extracellular Components Content Standards The learners demonstrate an understanding of (1) Composition of the endomembrane system; (2) Structure and function of organelles involved in energy transformation; (3) Structure and functions of the cytoskeleton; and, (4) Composition and functions of the extracellular components or matrix. Performance Standards The learners shall be able to construct three-dimensional models of whole cells using indigenous or recyclable materials. The models shall show the following cell parts: (1) Endomembrane System, (2) Mitochondria, and (3) Chloroplast Learning Competencies The learners: (1) explain the postulates of the cell theory (STEM_BIO11/12-1ac-1); (2) describe the structure and function of major and subcellular organelles (STEM_BIO11/12-Ia-c-2); (3) describe the structural components of the cell membrane (STEM_BIO11/12-Ig-h-11); and (4) relate the structure and composition of the cell membrane to its function (STEM_BIO11/12-Ig-h-12) Specific Learning Outcomes At the end of the unit lesson, the learners shall be able to: • • • • •
illustrate the structure of the endomembrane system, label its parts, and understand how the system works illustrate the structure of the mitochondria, label its parts, and understand the importance of the enfolding of the inner mitochondrial membrane illustrate the structure of the chloroplast, label its parts, and relate these parts to photosynthesis understand the connection of the endomembrane system to other cell parts such as the lysosomes, peroxisomes, endosomes, and cell membrane understand how the extracellular components or matrix determine the appearance and function of the tissues
LESSON OUTLINE Introduction Review on the differences between
5
prokaryotic and eukaryotic cells; submission and discussion of responses to the pre-topic homework assigned before the lecture.
Motivation
5
Brief class activity on prokaryotic and eukaryotic cells.
Instruction/ Lecture. Board work on cell parts, structure, Practice and function. Examination of cheek cells and
40
Hydrilla cells under a microscope. Class activity on identifying the parts and functions of the endomembrane system.
Enrichment Class discussion on cell size and relationship of surface area and volume
Evaluation
Assessment of learners’ knowledge; assignment of homework for next lecture
Materials
microscope (slide, cover slip), hand-held lens, work books, methylene blue, plastic spoon/popsicle stick, Hydrilla plansts, colored chalk/white board marker
5 5
Resources (continued at the end of Teaching Guide) (1) (n.d.). Retrieved from
(2) (n.d.). Retrieved from
INTRODUCTION (5 MINS)
Teacher Tip
1. Ask the learners to make a recap of the differences between prokaryotic and eukaryotic cells. 2. Discuss the learners’ responses to the pre-topic assignment on the functions of the following cell parts: • Nucleus
The review on the differences between prokaryotic and eukaryotic cells is needed to connect prerequisite knowledge to the present lesson. Remind the learners that the cell parts are found in eukaryotic cells. Remind the learners of the pre-topic assignment that shall be submitted before the lecture. This is to ensure the learners read on the topic before the lecture.
• Smooth Endoplasmic Reticulum • Rough Endoplasmic Reticulum • Golgi Apparatus • Ribosomes
Briefly discuss the structure of the cell membrane in order to provide basic knowledge on said structure to the learners. Do not fully elaborate on this topic since the structure and function of the cell membrane shall further be discussed in the succeeding parts of the lesson.
• Lysosomes • Mitochondria • Chloroplast 3. Present an overview of the cell membrane, its structure, and functions. 4. Define what an ‘organelle’ is and differentiate membrane-bound organelles from non-membranebound organelles. 5. Explain that in eukaryotic cells, the machinery of the cell is compartmentalized into organelles. The compartmentalization of the cell into membrane-bound organelles: • allows conflicting functions (i.e., synthesis vs. breakdown) and several cellular activities to occur simultaneously without interference from each other • separates the DNA material of the nucleus, mitochondria, and chloroplast • increases the surface area-volume ratio of the cell 6. Encourage the learners to look at the cell as both a system and subsystem. They should develop an understanding of how the parts of a cell interact with one another and how these parts help to do the ‘work’ of the cell (Source: (n.d.). Retrieved from )
10
The cell’s parts should be discussed as a system, emphasizing on the interconnectedness of each part to the others. To clarify common misconceptions, emphasize the following to the learners: • Not all organelles are surrounded by a membrane. • The plasma or cell membrane is different from the cell wall. • Not all cell parts are present in all kinds of cells.
MOTIVATION (5 MINS)
Briefly review the differences between prokaryotic and eukaryotic cells by asking questions to the learners. Sample question: What cell parts can be found in both prokaryotic and eukaryotic cells? Discuss the function/s of each part. Sample Responses: •
DNA
•
Cell membrane
•
Protoplasm (nucleoloid region and cytosol)
•
Ribosomes
Compare the cell to a big city. Ask the learners what the requirements of the city would be in order for it to function. Relate these requirements to the parts of the cell. Relate the learners’ responses to the functions of the different parts of a cell. Sample responses: •
The city will need power. What generates power for the city? Relate this to the function of the mitochondria and the chloroplast.
•
The city generates waste. How does it minimize its waste? How does the city handle its garbage? Relate this to the function of the lysosome.
•
The city requires raw materials to process into food, clothing, and housing materials. Where are these raw materials processed? Relate this to the functions of the Golgi Apparatus.
Compare animal cells from plant cells. For the animal cells, scrape cheek cells using a toothpick. Ask the learners to place the scrapings on a microscope slide and add a drop of water to the scrapings. Tease the scrapings into a thin layer and cover with a slip. Examine under HPO. Instruct the learners to draw the cells on their workbooks and to label the cell parts that they were able to observe under the microscope. For the plant cells, instruct the learners to obtain a Hydrilla leaf and place it on a microscope slide. Examine under LPO. Ask the learners to draw the cells on their workbooks and to label the cell parts that they were able to observe under the microscope.
Teacher tip If the number of available microscopes is limited, ask the learners to group themselves according to the number of microscopes available or set-up a demonstration scope for the whole class and facilitate the examination of cells so that all the learners will get a chance to observe the cells under the microscope. Orient the learners on the proper use and care of the microscopes, particularly on focusing first on LPO before shifting to HPO. Cheek cells are very transparent. Adjust the iris diaphragm or add a small amount of dye (i.e., methylene blue) to the scrapings. The learners will only see the cell membrane and the nucleus. Remind the learners to draw what they observe. Students may observe cytoplasmic streaming in the plant cell.
INSTRUCTION/PRACTICE (30 MINS) 1. Draw the cell membrane on one end of the board. 2. Draw the double membrane of the nucleus (nuclear membrane) on the other end of the board. 3. From the nuclear membrane, draw the reticulated structure of the endoplasmic reticulum. Ask the learners what the two types of endoplasmic reticulum are and their corresponding functions. 4. Draw the ribosomes as separate units. 5. Draw a DNA and an mRNA. Explain that the mRNA is a copy of the DNA that will be sent to the cytoplasm for protein synthesis. 6. Explain to the learners that the mRNA leaves the nucleus and goes to where the ribosomes are located (i.e., mRNA + functional ribosome) 7. Explain the possible ‘pathways’ for protein synthesis (e.g., within the cytosol or the endoplasmic reticulum) 8. Draw the mRNA + functional ribosome on the endoplasmic reticulum. With a lot of these, the endoplasmic reticulum becomes a rough endoplasmic reticulum. 9. Draw the formed polypeptide inside the rough endoplasmic reticulum. Discuss the formation of a cisternae and pinching off as a vesicle. 10. Draw the Golgi Apparatus and then a vesicle from the rough endoplasmic reticulum that travels to the Golgi Apparatus and attaches to the part which is nearest the rough endoplasmic reticulum. 11. Ask the learners what the function of the Golgi Apparatus is. Synthesize their answers and compare the Golgi Apparatus to a factory with an assembly manufacturing line. 12. Draw the polypeptide travelling along the Golgi Apparatus stack; pinching off as a vesicle to travel to the next stack. Repeat the process while increasing the complexity of the polypeptide drawing. 13. On the last stack, explain the ‘pathways’ that the vesicle may follow: become a lysosome through fusion with an endosome (i.e., formed by endocytosis), or travel to the cell membrane, fuse with it, and empty its contents. 14. Present the composition of the endomembrane system and discuss how these parts are connected to each other by structure and by function. 15. Draw the mitochondria and label its parts. Explain the importance of the enfolding (cristae) in increasing the surface area of the inner mitochondrial membrane. Further explain to the class that
Teacher tip Use chalk or white board markers with different colors. Explain the structure and function of each cell part as you draw them. Explain to the learners that a more detailed discussion of the structure and functions of the cell membrane, mitochondria, and chloroplast will be given in succeeding lessons.
enfolding is a common structural strategy to increase surface area. As an example, you may draw a cross-sectional structure of the small intestine. 16. Draw the chloroplast and label its parts. Explain the function that each part performs in the process of photosynthesis. 17. Discuss the similarities of the mitochondria and chloroplast (e.g., both are involved in energy transformation, both have DNA, high surface area, and double membranes).income accounts and lastly, expenses accounts.
Group the learners into pairs. Ask one to draw the endomembrane system as he/she explains it to his/her partner. Reshuffle the groupings and repeat until all learners have performed the exercise.
ENRICHMENT (30 MINS)
Facilitate a class discussion on why cells are generally small in size. Explain the relationship between surface area and volume.
EVALUATION (60 MINS
Ask questions to the learners. Sample questions can be found in the following electronic resources:
Teacher tip
• (n.d.). Retrieved from< http://www.proprofs.com/quiz-school/story.php?title=cell-structure-test > • (n.d.). Retrieved from< http://study.com/academy/exam/topic/cell-biology.html> Assign a research assignment on this question: How do environmental toxins like lead and mercury affect the functions of the cell? The assignment shall be submitted one week after this lesson.
Assignments should be handwritten.
RESOURCES (CONTINUED):
(4) (n.d.). Retrieved from (5) (n.d.). Retrieved from (6) (n.d.). Retrieved from (7) (n.d.). Retrieved from (8) (n.d.). Retrieved from
This strategy is aimed at ensuring that the learners have read the topic rather than just copying and printing from a source.
ASSESSMENT Learning Competency
Assessment Tool
Exemplary
Learner was able to Learner participation (during answer all the question/s without referring to his/ 1. describe the structure and lecture) her notes function of major and The learners shall be able to:
subcellular organelles (STEM_BIO11/12-Ia-c-2)
The learners shall be able to: 2. describe the structural components of the cell membrane (STEM_BIO11/12-Ig-h-11)
The learners shall be able to: 3. relate the structure and composition of the cell membrane to its function (STEM_BIO11/12-Ig-h12)
Assignment
Learner submitted an assignment beyond the requirements
Learner was able to Learner participation (during concisely answer all the questions practice)
Satisfactory
Developing
Learner was able to answer the main question without referring to his/her notes but was not able to answer follow-up question/s
Learner was able to answer the questions but he/she referred to his/her notes
(1) Learner was not able to answer the question/s
Learner submitted a comprehensive and wellwritten assignment
Learner submitted a well written report but some responses lack details
(1) Learner did not submit an assignment
Learner was able to answer the main question without referring to his/her notes but was not able to answer follow-up question/s
Learner was able to answer the questions but he/she referred to his/her notes
Learner submitted drawings that fulfilled the requirements (complete and detailed)
Learner submitted drawings that were incomplete
(1) Learner was not able to submit drawings (2) Learner’s drawings were haphazardly done Learner obtained less that 50% correct answers in the examination
Laboratory (Examination of Animal and Plant Cells)
Learner submitted drawings that were beyond the requirements
Examination
Learner obtained 90% to 100% correct answers in the examination
Learner obtained 70% to 89.99% correct answers in the examination
Learner obtained 50% to 69.99% correct answers in the examination
Research Assignment
Learner submitted a research assignment beyond the requirements
Learner submitted a comprehensive and wellwritten research assignment
Learner submitted a well written report but some responses lack details
14
Beginnning
(2) Learner read notes of his/her classmate
(2) Learner submitted a partially-finished assignment (1) Learner was not able to answer the question/s (2) Learner read notes of his/her classmate
(1) Learner did not submit an assignment (2) Learner submitted a partially-finished assignment
General Biology 1
60 MINS
Mitochondria and Chloroplasts Content Standards LESSON OUTLINE The learners demonstrate an understanding of the structure and function of the mitochondria and chloroplasts, the organelles involved in energy Introduction Review of relevant terminologies and definitions transformation.
5
Performance Standards The learners shall be able to construct three-dimensional models of whole cells using indigenous or recyclable materials. These models should show the mitochondria and chloroplasts.
Motivation
Instruction/ Discussion and lecture proper Delivery
30
Learning Competencies The learners describe the structure and function of major and subcellular organelles (STEM_BIO11/12-Ia-c-2) and distinguish prokaryotic and eukaryotic cells according to their distinguishing features (STEM_BIO11/12 -Ia-c-3)
Practice
10
5
Understanding of key concepts using real-life situations
Drawing (with label) activity
Enrichment Computation of surface area vs volume
5
Evaluation
5
Answering practice questions and homework
Resources (continued at the end of Teaching Guide) Specific Learning Outcomes At the end of the lesson, the learners shall be able to: • •
illustrate the structure of the mitochondria, label its parts, and understand the importance of the enfolding of the inner mitochondrial membrane illustrate the structure of the chloroplast, label its parts, and relate these parts to photosynthesis
(1) http://scienceaid.co.uk/biology/biochemistry/atp.html (2) http://www.britannica.com/list/6-cell-organelles)
(3) http://www.nature.com/scitable/topicpage/mitochondria-14053590) (4) http://www.britannica.com/list/6-cell-organelles (5) http://www.nature.com/scitable/topicpage/mitochondria-14053590) (6) http://biology.tutorvista.com/animal-and-plant-cells/chloroplasts.html (7) ttp://www.nature.com/scitable/topicpage/mitochondria-14053590
INTRODUCTION (5 MINS)
Facilitate a review of the following concepts: • • • • •
Differences between prokaryotic and eukaryotic cells Definition of an ‘organelle’ Differences between membrane-bound organelles and non-membrane-bound organelles Functions of the different parts of a cell The endomembrane system
MEMBRANE-BOUND ORGANELLES
NON-MEMBRANE-BOUND ORGANELLES
Nucleus
Ribosomes
Smooth ER
Centrioles
Rough ER
Cytoskeleton
Golgi Apparatus Vacuoles and Vesicles Mitochondria Chloroplast and other plastids Lysosomes Peroxisomes
Explain that in eukaryotic cells, the machinery of the cell is compartmentalized into organelles. The compartmentalization of the cell into membrane-bound organelles: • • •
allows conflicting functions (i.e., synthesis vs. breakdown) and several cellular activities to occur simultaneously without interference from each other separates the DNA material of the nucleus, mitochondria, and chloroplast increases the surface area-volume ratio of the cell
16
Encourage the learners to look at the cell as both a system and subsystem. They should develop an understanding of how the parts of a cell interact with one another and how these parts help to do the ‘work’ of the cell (Source: (n.d.). Retrieved from ) Emphasize to the learners that energy transformation is one of the characteristics of life. This refers to the ability to obtain and use energy. This characterizes the main function of the mitochondria and the chloroplasts.
MOTIVATION (5 MINS)
Ask the learners how they understand the concept of compartmentalization. Relate the concept to how the cell is compartmentalized into organelles. Compare compartmentalization to the division of a house into a receiving room or sala, kitchen, dining room, comfort rooms, bedrooms, etc. Teacher tip Ask the learners why they think a house is divided into several rooms. A possible response is that partitioning of the house into different parts facilitates the simultaneous occurrence of several activities without interfering with one another. Also, materials needed for each activity can be stored at their specific areas. For example, pots and pans are being stored in the kitchen and not in the bedroom. Beds and pillows are found in the bedroom and not in the toilet/bath. Explain to the learners that the mitochondria and chloroplasts have a small amount of DNA. Although most of the proteins of these organelles are imported from the cytosol and are thus programmed by the nuclear DNA, their DNA programs the synthesis of the proteins made on the organelles’ ribosomes (Source: Campbell et al). Compartmentalization separates the DNA material of the nucleus, mitochondria, and chloroplast. Ask the learners if they have experienced going to a city/municipal hall and if they have observed that the Mayor, Vice-Mayor, and the City/Municipal Administrator have separate offices. You can use other examples such as the University President, VP for Academic Affairs, VP for Finance; Philippine President, Vice President, Senators, etc. Compare the nuclear DNA to the Mayor and the mitochondrial DNA and chloroplast DNA to the Vice
Explain to the learner that this is how the cell is able to allow conflicting functions (e.g., synthesis vs breakdown) and several cellular activities to occur simultaneously without interference from each other.
Mayor. The Mayor runs the city/municipality but the Vice Mayor also performs functions that are specific to their positions. They need different offices (or compartments) to avoid conflict in their functions.
Teacher tip Select a fruit that can be easily peeled like calamansi or dalandan
Introduce the concept of surface area-volume ratio/relationship to the learners. Show a fruit to the learners and explain that the outer surface of the fruit is the surface area. Peel the fruit and show them what’s inside, explaining that the inside of the fruit is the volume. Explain to the learners that surface area (SA) and volume (V) do not increase in the same manner. As an object increases in size, its volume increases as the cube of its linear dimensions while surface area increases as the square of its linear dimensions. Example: If the initial starting point is the same: SA = 2; Volume = 2 (Ratio = 1:1) A one-step increase will result to: SA = 22 = 4 while V = 23 = 8 (Ratio = 1:2) Teacher tip Ask questions to the learners while giving the lecture.
INSTRUCTION/DELIVERY (30 MINS) Explain and discuss the nature and functions of the Adenosine Triphosphate (ATP) to the learners. Adenosine Triphosphate (ATP)—It is the major energy currency of the cell that provides the energy for most of the energy-consuming activities of the cell. The ATP regulates many biochemical pathways. Mechanism: When the third phosphate group of ATP is removed by hydrolysis, a substantial amount of free energy is released. ATP + H2O → ADP + Pi where ADP is adenosine diphosphate and Pi is inorganic phosphate Group the learners into pairs. Ask one to draw the endomembrane system as he/she explains it to his/ her partner. Reshuffle the groupings and repeat until all learners have performed the exercise.
18
If an LCD projector is not available, draw the structure of the mitochondria and chloroplast on the board.
Illustration 1: Energy release in Hydrolysis (Source: (n.d.). Retrieved from http://scienceaid.co.uk/biology/biochemistry/atp.html)
Illustration 2: Chemical Energy and ATP (Source: (n.d.). Retrieved from http://winklebiology.weebly.com/chemical-energyatp.html) Synthesis of ATP • ADP + Pi → ATP + H2O • requires energy: 7.3 kcal/mole • occurs in the cytosol by glycolysis
• •
occurs in mitochondria by cellular respiration occurs in chloroplasts by photosynthesis
Consumption of ATP ATP powers most energy-consuming activities of cells, such as: • • • • • • • •
anabolic (synthesis) reactions, such as: joining transfer RNAs to amino acids for assembly into proteins synthesis of nucleoside triphosphates for assembly into DNA and RNA synthesis of polysaccharides synthesis of fats active transport of molecules and ions conduction of nerve impulses maintenance of cell volume by osmosis
•
addition of phosphate groups (phosphorylation) to different proteins (e.g., to alter their activity in cell signaling)
• • •
muscle contraction beating of cilia and flagella (including sperm) bioluminescence
Extracellular ATP In mammals, ATP also functions outside of cells. ATP is released in the following examples: • • • •
from damaged cells to elicit inflammation and pain from the carotid body to signal a shortage of oxygen in the blood from taste receptor cells to trigger action potentials in the sensory nerves leading back to the brain from the stretched wall of the urinary bladder to signal when the bladder needs emptying
In eukaryotic cells, the mitochondria and chloroplasts are the organelles that convert energy to other forms which cells can use for their functions. Discuss the function and structure of the mitochondria.
20
Mitochondria (singular, mitochondrion)—Mitochondria are the sites of cellular respiration, the metabolic process that uses oxygen to drive the generation of ATP by extracting energy from sugars, fats, and other fuels. The mitochondria are oval-shaped organelles found in most eukaryotic cells. They are considered to be the ‘powerhouses’ of the cell. As the site of cellular respiration, mitochondria serve to transform molecules such as glucose into an energy molecule known as adenosine triphosphate (ATP). ATP fuels cellular processes by breaking its high-energy chemical bonds. Mitochondria are most plentiful in cells that require significant amounts of energy to function, such as liver and muscle cells. Figure 1: Structure of the Mitochonsdria (Source: (n.d.). Retrieved from http://www.britannica.com/list/ 6-cell-organelles) The mitochondria has two membranes that are similar in composition to the cell membrane: •
•
Outer membrane—is a selectively permeable membrane that surrounds the mitochondria. It is the site of attachment for the respiratory assembly of the electron transport chain and ATP Synthase. It has integral proteins and pores for transporting molecules just like the cell membrane Inner membrane—folds inward (called cristae) to increase surfaces for cellular metabolism. It contains ribosomes and the DNA of the mitochondria. The inner membrane creates two enclosed spaces within the mitochondria: • intermembrane space between the outer membrane and the inner membrane; and • matrix that is enclosed within the inner membrane.
Ask questions to the learners on the structure of the mitochondria. A sample question could be: What is the importance of the enfolding of the mitochondria? The response would be to increase the surface area that can be ‘packed’ into such a small space. Discuss the purpose of the mitochondrial membranes.
22
As mentioned, the mitochondria has two membranes: the outer and inner mitochondrial membranes. •
•
Outer Membrane • fully surrounds the inner membrane, with a small intermembrane space in between • has many protein-based pores that are big enough to allow the passage of ions and molecules as large as a small protein Inner membrane • has restricted permeability like the plasma membrane • is loaded with proteins involved in electron transport and ATP synthesis • surrounds the mitochondrial matrix, where the citric acid cycle produces the electrons that travel from one protein complex to the next in the inner membrane. At the end of this electron transport chain, the final electron acceptor is oxygen, and this ultimately forms water (H20). At the same time, the electron transport chain produces ATP in a process called oxidative phosphorylation
During electron transport, the participating protein complexes push protons from the matrix out to the intermembrane space. This creates a concentration gradient of protons that another protein complex, called ATP synthase, uses to power synthesis of the energy carrier molecule ATP. Figure 4: The Electrochemical Proton Gradient and the ATP Synthase (Source: (n.d.). Retrieved from http://www.nature.com/scitable/topicpage/mitochondria-14053590) Explain and discuss the structure and functions of the Chloroplasts. Chloroplasts—Chloroplasts, which are found in plants and algae, are the sites of photosynthesis. This process converts solar energy to chemical energy by absorbing sunlight and using it to drive the synthesis of organic compounds such as sugars from carbon dioxide and water. The word chloroplast is derived from the Greek word chloros which means ‘green’ and plastes which means ‘the one who forms’. The chloroplasts are cellular organelles of green plants and some eukaryotic organisms. These organelles conduct photosynthesis. They absorb sunlight and convert it into sugar molecules. They also produce free energy stored in the form of ATP and NADPH through photosynthesis. Chloroplasts are double membrane-bound organelles and are the sites of photosynthesis. The
22
Teacher tip
Lecture on mitochondrial membranes can be accessed at (n.d.). Retrieved from .
chloroplast has a system of three membranes: the outer membrane, the inner membrane, and the thylakoid system. The outer and the inner membranes of the chloroplast enclose a semi-gel-like fluid known as the stroma. The stroma makes up much of the volume of the chloroplast. The thylakoid system floats in the stroma. Structure of the Chloroplast • • •
•
•
Outer membrane—This is a semi-porous membrane and is permeable to small molecules and ions which diffuse easily. The outer membrane is not permeable to larger proteins. Intermembrane Space—This is usually a thin intermembrane space about 10-20 nanometers and is present between the outer and the inner membrane of the chloroplast. Inner membrane—The inner membrane of the chloroplast forms a border to the stroma. It regulates passage of materials in and out of the chloroplast. In addition to the regulation activity, fatty acids, lipids and carotenoids are synthesized in the inner chloroplast membrane. Stroma—This is an alkaline, aqueous fluid that is protein-rich and is present within the inner membrane of the chloroplast. It is the space outside the thylakoid space. The chloroplast DNA, chloroplast ribosomes, thylakoid system, starch granules, and other proteins are found floating around the stroma. Thylakoid System
The thylakoid system is suspended in the stroma. It is a collection of membranous sacks called thylakoids. Thylakoids are small sacks that are interconnected. The membranes of these thylakoids are the sites for the light reactions of the photosynthesis to take place. The chlorophyll is found in the thylakoids. The thylakoids are arranged in stacks known as grana. Each granum contains around 10-20 thylakoids. The word thylakoid is derived from the Greek word thylakos which means 'sack'. Important protein complexes which carry out the light reaction of photosynthesis are embedded in the membranes of the thylakoids.
The Photosystem I and the Photosystem II are
Teacher tip If an LCD projector is not available, draw the structure of the chloroplast on the board.
Lecture on structure and functions of the chloroplast can be accessed at (n.d.). Retrieved from .
complexes that harvest light with chlorophyll and carotenoids. They absorb the light energy and use it to energize the electrons. The molecules present in the thylakoid membrane use the electrons that are energized to pump hydrogen ions into the thylakoid space. This decreases the pH and causes it to become acidic in nature. A large protein complex known as the ATP synthase controls the concentration gradient of the hydrogen ions in the thylakoid space to generate ATP energy. The hydrogen ions flow back into the stroma.
PRACTICE (10 MINS)
Thylakoids are of two types: granal thylakoids and stromal thylakoids. Granal thylakoids are arranged in the grana. These circular discs that are about 300-600 nanometers in diameter. The stromal thylakoids are in contact with the stroma and are in the form of helicoid sheets.
Group the learners into pairs. Ask one to draw the mitochondria and label its parts while the other does the same for chloroplast. Once done, the partners exchange tasks (i.e., the learner that drew the mitochondria now does the same for the chloroplast).
The granal thylakoids contain only Photosystem II protein complex. This allows them to stack tightly and form many granal layers with granal membrane. This structure increases stability and surface area for the capture of light.
Reproduce these diagrams without the labels and use these for the class activity. To demonstrate how folding increases surface area, ask the learners to trace the edges of the outer membrane with a thread and measure the length of the thread afterwards. Repeat the same for the inner membrane. Compare the results and discuss how the enfolding of the inner membrane increases surface area through folding.
The Photosystem I and ATP synthase protein complexes are present in the stroma. These protein complexes act as spacers between the sheets of stromal thylakoids.
24
ENRICHMENT (30 MINS)
1. Using the figure below, ask learners to compute surface area vs. volume. 2. Draw the table on the board and instruct the learners to write their measurements.
Teacher tip
EVALUATION (60 MINS)
Ask the learners to answer practice questions on the following electronic resources: • • • • •
Clarify to the learners the misconception that the appearance of organelles are static and rigid.
http://www.mcqbiology.com/2013/03/multiple-choice-questions-on_25.html#.Vl7Uq3YrLrc http://www.uic.edu/classes/bios/bios100/summer2004/samples02.htm http://www.tutorvista.com/content/science/science-i/fundamental-unit-life/question-answers-1.php http://www.buzzfeed.com/kellyoakes/the-mitochondria-is-the-powerhouse-of-the-cell#.fajAl0b6o http://global.oup.com/uk/orc/biosciences/cellbiology/wang/student/mcqs/ch10/
Possible responses to the homework (Source: Campbell et al, 10th Ed.): They have double membranes and are not part of the endomembrane system. Their shape is changeable. They are autonomous (somewhat independent) organelles that grow and occasionally pinch in two, thereby reproducing themselves. • They are mobile and move around the cell along tracks of the cytoskeleton, a structural network of the cell. • They contain ribosomes, as well as multiple circular DNA molecules associated with their inner membranes. The DNA in these organelles programs the synthesis of some organelle proteins on ribosomes that have been synthesized and assembled there as well. 2. Give out the homework for next meeting. • • •
What are the characteristics shared by these two energy transforming organelles? Instruct the learners to write an essay on probable reasons for these the shared characteristics of the mitochondria and the chloroplast. Learners shall submit a handwritten essay on the Endosymbiotic Theory and how it explains the similarity between the mitochondria and chloroplast.
26
Teacher tip Check the electronic resources on Endosymbiotic Theory: https://www.youtube.com/watch? v=bBjD4A7R2xU (Endosymbiotic Theory in plain English) https://www.youtube.com/watch?v=FQmAnmLZtE
EVALUATION Learning Competency
Assessment Tool
The learners shall be able to describe the following:
Learner participation (during lecture)
1. structure and function of major and subcellular organelles (STEM_BIO11/12-Iac-2)
Assignment
Examination
Exemplary
Satisfactory
Developing
Learner was able to answer all the question/ s without referring to his/her notes
Learner was able to answer the main question without referring to his/ her notes but was not able to answer follow-up question/s
Learner was able to answer the questions but he/ she referred to his/ her notes
(1) Learner was not able to answer the question/s
Learner submitted an assignment beyond the requirements
Learner submitted a comprehensive and wellwritten assignment
Learner submitted a well written report but some responses lack details
(1) Learner did not submit an assignment
Learner obtained 70% to 89.99% correct answers in the examination
Learner obtained 50% to 69.99% correct answers in the examination
Learner obtained less that 50% correct answers in the examination
Learner submitted an essay that was comprehensive and wellwritten
Learner submitted a well-written essay some details are lacking
(1) Learner did not submit an essay
Learner obtained 90% to 100% correct answers in the examination
Essay Assignment Learner submitted an essay beyond the requirements
Beginnning
(2) Learner read notes of his/her classmate
(2) Learner submitted a partially-finished assignment
(2) Learner submitted a partially-finished essay
General Biology 1
60 MINS
Mitochondria and Chloroplasts Content Standards LESSON OUTLINE The learners demonstrate an understanding of the structure and function of the mitochondria and chloroplasts, the organelles involved in energy Introduction Review of relevant terminologies and definitions transformation.
5
Performance Standards The learners shall be able to construct three-dimensional models of whole cells using indigenous or recyclable materials. These models should show the mitochondria and chloroplasts.
Motivation
Instruction/ Discussion and lecture proper Delivery
30
Learning Competencies The learners describe the structure and function of major and subcellular organelles (STEM_BIO11/12-Ia-c-2) and distinguish prokaryotic and eukaryotic cells according to their distinguishing features (STEM_BIO11/12 -Ia-c-3)
Practice
10
5
Understanding of key concepts using real-life situations
Drawing (with label) activity
Enrichment Computation of surface area vs volume
5
Evaluation
5
Answering practice questions and homework
Resources (continued at the end of Teaching Guide) Specific Learning Outcomes At the end of the lesson, the learners shall be able to: • •
illustrate the structure of the mitochondria, label its parts, and understand the importance of the enfolding of the inner mitochondrial membrane illustrate the structure of the chloroplast, label its parts, and relate these parts to photosynthesis
(1) http://scienceaid.co.uk/biology/biochemistry/atp.html (2) http://www.britannica.com/list/6-cell-organelles)
(3) http://www.nature.com/scitable/topicpage/mitochondria-14053590) (4) http://www.britannica.com/list/6-cell-organelles (5) http://www.nature.com/scitable/topicpage/mitochondria-14053590) (6) http://biology.tutorvista.com/animal-and-plant-cells/chloroplasts.html (7) ttp://www.nature.com/scitable/topicpage/mitochondria-14053590
INTRODUCTION (5 MINS)
Facilitate a review of the following concepts: • • • • •
Differences between prokaryotic and eukaryotic cells Definition of an ‘organelle’ Differences between membrane-bound organelles and non-membrane-bound organelles Functions of the different parts of a cell The endomembrane system
MEMBRANE-BOUND ORGANELLES
NON-MEMBRANE-BOUND ORGANELLES
Nucleus
Ribosomes
Smooth ER
Centrioles
Rough ER
Cytoskeleton
Golgi Apparatus Vacuoles and Vesicles Mitochondria Chloroplast and other plastids Lysosomes Peroxisomes
Explain that in eukaryotic cells, the machinery of the cell is compartmentalized into organelles. The compartmentalization of the cell into membrane-bound organelles: • • •
allows conflicting functions (i.e., synthesis vs. breakdown) and several cellular activities to occur simultaneously without interference from each other separates the DNA material of the nucleus, mitochondria, and chloroplast increases the surface area-volume ratio of the cell
16
Encourage the learners to look at the cell as both a system and subsystem. They should develop an understanding of how the parts of a cell interact with one another and how these parts help to do the ‘work’ of the cell (Source: (n.d.). Retrieved from ) Emphasize to the learners that energy transformation is one of the characteristics of life. This refers to the ability to obtain and use energy. This characterizes the main function of the mitochondria and the chloroplasts.
MOTIVATION (5 MINS)
Ask the learners how they understand the concept of compartmentalization. Relate the concept to how the cell is compartmentalized into organelles. Compare compartmentalization to the division of a house into a receiving room or sala, kitchen, dining room, comfort rooms, bedrooms, etc. Teacher tip Ask the learners why they think a house is divided into several rooms. A possible response is that partitioning of the house into different parts facilitates the simultaneous occurrence of several activities without interfering with one another. Also, materials needed for each activity can be stored at their specific areas. For example, pots and pans are being stored in the kitchen and not in the bedroom. Beds and pillows are found in the bedroom and not in the toilet/bath. Explain to the learners that the mitochondria and chloroplasts have a small amount of DNA. Although most of the proteins of these organelles are imported from the cytosol and are thus programmed by the nuclear DNA, their DNA programs the synthesis of the proteins made on the organelles’ ribosomes (Source: Campbell et al). Compartmentalization separates the DNA material of the nucleus, mitochondria, and chloroplast. Ask the learners if they have experienced going to a city/municipal hall and if they have observed that the Mayor, Vice-Mayor, and the City/Municipal Administrator have separate offices. You can use other examples such as the University President, VP for Academic Affairs, VP for Finance; Philippine President, Vice President, Senators, etc. Compare the nuclear DNA to the Mayor and the mitochondrial DNA and chloroplast DNA to the Vice
Explain to the learner that this is how the cell is able to allow conflicting functions (e.g., synthesis vs breakdown) and several cellular activities to occur simultaneously without interference from each other.
Mayor. The Mayor runs the city/municipality but the Vice Mayor also performs functions that are specific to their positions. They need different offices (or compartments) to avoid conflict in their functions.
Teacher tip Select a fruit that can be easily peeled like calamansi or dalandan
Introduce the concept of surface area-volume ratio/relationship to the learners. Show a fruit to the learners and explain that the outer surface of the fruit is the surface area. Peel the fruit and show them what’s inside, explaining that the inside of the fruit is the volume. Explain to the learners that surface area (SA) and volume (V) do not increase in the same manner. As an object increases in size, its volume increases as the cube of its linear dimensions while surface area increases as the square of its linear dimensions. Example: If the initial starting point is the same: SA = 2; Volume = 2 (Ratio = 1:1) A one-step increase will result to: SA = 22 = 4 while V = 23 = 8 (Ratio = 1:2) Teacher tip Ask questions to the learners while giving the lecture.
INSTRUCTION/DELIVERY (30 MINS) Explain and discuss the nature and functions of the Adenosine Triphosphate (ATP) to the learners. Adenosine Triphosphate (ATP)—It is the major energy currency of the cell that provides the energy for most of the energy-consuming activities of the cell. The ATP regulates many biochemical pathways. Mechanism: When the third phosphate group of ATP is removed by hydrolysis, a substantial amount of free energy is released. ATP + H2O → ADP + Pi where ADP is adenosine diphosphate and Pi is inorganic phosphate Group the learners into pairs. Ask one to draw the endomembrane system as he/she explains it to his/ her partner. Reshuffle the groupings and repeat until all learners have performed the exercise.
18
If an LCD projector is not available, draw the structure of the mitochondria and chloroplast on the board.
Illustration 1: Energy release in Hydrolysis (Source: (n.d.). Retrieved from http://scienceaid.co.uk/biology/biochemistry/atp.html)
Illustration 2: Chemical Energy and ATP (Source: (n.d.). Retrieved from http://winklebiology.weebly.com/chemical-energyatp.html) Synthesis of ATP • ADP + Pi → ATP + H2O • requires energy: 7.3 kcal/mole • occurs in the cytosol by glycolysis
• •
occurs in mitochondria by cellular respiration occurs in chloroplasts by photosynthesis
Consumption of ATP ATP powers most energy-consuming activities of cells, such as: • • • • • • • •
anabolic (synthesis) reactions, such as: joining transfer RNAs to amino acids for assembly into proteins synthesis of nucleoside triphosphates for assembly into DNA and RNA synthesis of polysaccharides synthesis of fats active transport of molecules and ions conduction of nerve impulses maintenance of cell volume by osmosis
•
addition of phosphate groups (phosphorylation) to different proteins (e.g., to alter their activity in cell signaling)
• • •
muscle contraction beating of cilia and flagella (including sperm) bioluminescence
Extracellular ATP In mammals, ATP also functions outside of cells. ATP is released in the following examples: • • • •
from damaged cells to elicit inflammation and pain from the carotid body to signal a shortage of oxygen in the blood from taste receptor cells to trigger action potentials in the sensory nerves leading back to the brain from the stretched wall of the urinary bladder to signal when the bladder needs emptying
In eukaryotic cells, the mitochondria and chloroplasts are the organelles that convert energy to other forms which cells can use for their functions. Discuss the function and structure of the mitochondria.
20
Mitochondria (singular, mitochondrion)—Mitochondria are the sites of cellular respiration, the metabolic process that uses oxygen to drive the generation of ATP by extracting energy from sugars, fats, and other fuels. The mitochondria are oval-shaped organelles found in most eukaryotic cells. They are considered to be the ‘powerhouses’ of the cell. As the site of cellular respiration, mitochondria serve to transform molecules such as glucose into an energy molecule known as adenosine triphosphate (ATP). ATP fuels cellular processes by breaking its high-energy chemical bonds. Mitochondria are most plentiful in cells that require significant amounts of energy to function, such as liver and muscle cells. Figure 1: Structure of the Mitochonsdria (Source: (n.d.). Retrieved from http://www.britannica.com/list/ 6-cell-organelles) The mitochondria has two membranes that are similar in composition to the cell membrane: •
•
Outer membrane—is a selectively permeable membrane that surrounds the mitochondria. It is the site of attachment for the respiratory assembly of the electron transport chain and ATP Synthase. It has integral proteins and pores for transporting molecules just like the cell membrane Inner membrane—folds inward (called cristae) to increase surfaces for cellular metabolism. It contains ribosomes and the DNA of the mitochondria. The inner membrane creates two enclosed spaces within the mitochondria: • intermembrane space between the outer membrane and the inner membrane; and • matrix that is enclosed within the inner membrane.
Ask questions to the learners on the structure of the mitochondria. A sample question could be: What is the importance of the enfolding of the mitochondria? The response would be to increase the surface area that can be ‘packed’ into such a small space. Discuss the purpose of the mitochondrial membranes.
22
As mentioned, the mitochondria has two membranes: the outer and inner mitochondrial membranes. •
•
Outer Membrane • fully surrounds the inner membrane, with a small intermembrane space in between • has many protein-based pores that are big enough to allow the passage of ions and molecules as large as a small protein Inner membrane • has restricted permeability like the plasma membrane • is loaded with proteins involved in electron transport and ATP synthesis • surrounds the mitochondrial matrix, where the citric acid cycle produces the electrons that travel from one protein complex to the next in the inner membrane. At the end of this electron transport chain, the final electron acceptor is oxygen, and this ultimately forms water (H20). At the same time, the electron transport chain produces ATP in a process called oxidative phosphorylation
During electron transport, the participating protein complexes push protons from the matrix out to the intermembrane space. This creates a concentration gradient of protons that another protein complex, called ATP synthase, uses to power synthesis of the energy carrier molecule ATP. Figure 4: The Electrochemical Proton Gradient and the ATP Synthase (Source: (n.d.). Retrieved from http://www.nature.com/scitable/topicpage/mitochondria-14053590) Explain and discuss the structure and functions of the Chloroplasts. Chloroplasts—Chloroplasts, which are found in plants and algae, are the sites of photosynthesis. This process converts solar energy to chemical energy by absorbing sunlight and using it to drive the synthesis of organic compounds such as sugars from carbon dioxide and water. The word chloroplast is derived from the Greek word chloros which means ‘green’ and plastes which means ‘the one who forms’. The chloroplasts are cellular organelles of green plants and some eukaryotic organisms. These organelles conduct photosynthesis. They absorb sunlight and convert it into sugar molecules. They also produce free energy stored in the form of ATP and NADPH through photosynthesis. Chloroplasts are double membrane-bound organelles and are the sites of photosynthesis. The
22
Teacher tip
Lecture on mitochondrial membranes can be accessed at (n.d.). Retrieved from .
chloroplast has a system of three membranes: the outer membrane, the inner membrane, and the thylakoid system. The outer and the inner membranes of the chloroplast enclose a semi-gel-like fluid known as the stroma. The stroma makes up much of the volume of the chloroplast. The thylakoid system floats in the stroma. Structure of the Chloroplast • • •
•
•
Outer membrane—This is a semi-porous membrane and is permeable to small molecules and ions which diffuse easily. The outer membrane is not permeable to larger proteins. Intermembrane Space—This is usually a thin intermembrane space about 10-20 nanometers and is present between the outer and the inner membrane of the chloroplast. Inner membrane—The inner membrane of the chloroplast forms a border to the stroma. It regulates passage of materials in and out of the chloroplast. In addition to the regulation activity, fatty acids, lipids and carotenoids are synthesized in the inner chloroplast membrane. Stroma—This is an alkaline, aqueous fluid that is protein-rich and is present within the inner membrane of the chloroplast. It is the space outside the thylakoid space. The chloroplast DNA, chloroplast ribosomes, thylakoid system, starch granules, and other proteins are found floating around the stroma. Thylakoid System
The thylakoid system is suspended in the stroma. It is a collection of membranous sacks called thylakoids. Thylakoids are small sacks that are interconnected. The membranes of these thylakoids are the sites for the light reactions of the photosynthesis to take place. The chlorophyll is found in the thylakoids. The thylakoids are arranged in stacks known as grana. Each granum contains around 10-20 thylakoids. The word thylakoid is derived from the Greek word thylakos which means 'sack'. Important protein complexes which carry out the light reaction of photosynthesis are embedded in the membranes of the thylakoids.
The Photosystem I and the Photosystem II are
Teacher tip If an LCD projector is not available, draw the structure of the chloroplast on the board.
Lecture on structure and functions of the chloroplast can be accessed at (n.d.). Retrieved from .
complexes that harvest light with chlorophyll and carotenoids. They absorb the light energy and use it to energize the electrons. The molecules present in the thylakoid membrane use the electrons that are energized to pump hydrogen ions into the thylakoid space. This decreases the pH and causes it to become acidic in nature. A large protein complex known as the ATP synthase controls the concentration gradient of the hydrogen ions in the thylakoid space to generate ATP energy. The hydrogen ions flow back into the stroma.
PRACTICE (10 MINS)
Thylakoids are of two types: granal thylakoids and stromal thylakoids. Granal thylakoids are arranged in the grana. These circular discs that are about 300-600 nanometers in diameter. The stromal thylakoids are in contact with the stroma and are in the form of helicoid sheets.
Group the learners into pairs. Ask one to draw the mitochondria and label its parts while the other does the same for chloroplast. Once done, the partners exchange tasks (i.e., the learner that drew the mitochondria now does the same for the chloroplast).
The granal thylakoids contain only Photosystem II protein complex. This allows them to stack tightly and form many granal layers with granal membrane. This structure increases stability and surface area for the capture of light.
Reproduce these diagrams without the labels and use these for the class activity. To demonstrate how folding increases surface area, ask the learners to trace the edges of the outer membrane with a thread and measure the length of the thread afterwards. Repeat the same for the inner membrane. Compare the results and discuss how the enfolding of the inner membrane increases surface area through folding.
The Photosystem I and ATP synthase protein complexes are present in the stroma. These protein complexes act as spacers between the sheets of stromal thylakoids.
24
ENRICHMENT (30 MINS)
1. Using the figure below, ask learners to compute surface area vs. volume. 2. Draw the table on the board and instruct the learners to write their measurements.
Teacher tip
EVALUATION (60 MINS)
Ask the learners to answer practice questions on the following electronic resources: • • • • •
Clarify to the learners the misconception that the appearance of organelles are static and rigid.
http://www.mcqbiology.com/2013/03/multiple-choice-questions-on_25.html#.Vl7Uq3YrLrc http://www.uic.edu/classes/bios/bios100/summer2004/samples02.htm http://www.tutorvista.com/content/science/science-i/fundamental-unit-life/question-answers-1.php http://www.buzzfeed.com/kellyoakes/the-mitochondria-is-the-powerhouse-of-the-cell#.fajAl0b6o http://global.oup.com/uk/orc/biosciences/cellbiology/wang/student/mcqs/ch10/
Possible responses to the homework (Source: Campbell et al, 10th Ed.): They have double membranes and are not part of the endomembrane system. Their shape is changeable. They are autonomous (somewhat independent) organelles that grow and occasionally pinch in two, thereby reproducing themselves. • They are mobile and move around the cell along tracks of the cytoskeleton, a structural network of the cell. • They contain ribosomes, as well as multiple circular DNA molecules associated with their inner membranes. The DNA in these organelles programs the synthesis of some organelle proteins on ribosomes that have been synthesized and assembled there as well. 2. Give out the homework for next meeting. • • •
What are the characteristics shared by these two energy transforming organelles? Instruct the learners to write an essay on probable reasons for these the shared characteristics of the mitochondria and the chloroplast. Learners shall submit a handwritten essay on the Endosymbiotic Theory and how it explains the similarity between the mitochondria and chloroplast.
26
Teacher tip Check the electronic resources on Endosymbiotic Theory: https://www.youtube.com/watch? v=bBjD4A7R2xU (Endosymbiotic Theory in plain English) https://www.youtube.com/watch?v=FQmAnmLZtE
EVALUATION Learning Competency
Assessment Tool
The learners shall be able to describe the following:
Learner participation (during lecture)
1. structure and function of major and subcellular organelles (STEM_BIO11/12-Iac-2)
Assignment
Examination
Exemplary
Satisfactory
Developing
Learner was able to answer all the question/ s without referring to his/her notes
Learner was able to answer the main question without referring to his/ her notes but was not able to answer follow-up question/s
Learner was able to answer the questions but he/ she referred to his/ her notes
(1) Learner was not able to answer the question/s
Learner submitted an assignment beyond the requirements
Learner submitted a comprehensive and wellwritten assignment
Learner submitted a well written report but some responses lack details
(1) Learner did not submit an assignment
Learner obtained 70% to 89.99% correct answers in the examination
Learner obtained 50% to 69.99% correct answers in the examination
Learner obtained less that 50% correct answers in the examination
Learner submitted an essay that was comprehensive and wellwritten
Learner submitted a well-written essay some details are lacking
(1) Learner did not submit an essay
Learner obtained 90% to 100% correct answers in the examination
Essay Assignment Learner submitted an essay beyond the requirements
Beginnning
(2) Learner read notes of his/her classmate
(2) Learner submitted a partially-finished assignment
(2) Learner submitted a partially-finished essay
General Biology 1
180 MINS
Structure and Functions of Animal Tissues and Cell Modification LESSON OUTLINE
Content Standard The learners demonstrate an understanding of animal tissues and cell modification.
Introduction Communicating learning objectives to the learners.
Performance Standard Motivation The learners shall be able to construct a three-dimensional model of the animal tissue by using recyclable or indigenous materials. Learning Competencies The learners:
Specific Learning Outcomes At the end of the lesson, the learners shall be able to:
•
10
Instruction/ Review on the Hierarchy of Biological Organisation and PTSF; Lesson on Animal Delivery
95
Practice
Class Activity: Reporting on structure and function of animal tissue or showing of infomercial on diseases.
60
Evaluation
Class Quiz
10
Tissues and on Cell Modfication
• classify different cell types (plant/animal tissue) and specify the functions of each (STEM_BIO11/12-Ia-c-4) • describe some cell modifications that lead to adaptation to carry out specialized functions (e.g., microvilli, root hair) (STEM_BIO11/12-Ia-c-5)
•
Class Activity: Pinoy Henyo Classroom Edition
5
Materials
present a five-minute report on how the structures of different animal tissues define their function or show a two-minute infomercial about a disease that is caused by animal tissue malfunction; provide insights, offer constructive feedback, and note areas of improvement on their classmates’ reports or infomercial
microscopes, LCD Projector (if available), laptop or computer (if available), manila paper, cartolina, photos, images, or illustrations of different types of tissues, drawing materials (e.g. pens, pencils, paper, color pencils, etc.) Resources (continued at the end of Teaching Guide)
(1) Reece JB, U. L., (2010). Campbell Biology 10th. San Francisco (CA).
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INTRODUCTION (5 MINS)
Introduce the following learning objectives by flashing these on the board: • •
classify different cell types (plant/animal tissue) and specify the functions of each (STEM_BIO11/12Ia-c-4) describe some cell modifications that lead to adaptation to carry out specialized functions (e.g., microvilli, root hair) (STEM_BIO11/12-Ia-c-5)
Ask the learners to work in pairs and write the learning objectives using their own words.
MOTIVATION (10 MINS) PINOY HENYO CLASSROOM EDITION Divide the class into two groups. Explain to the learners that instead of having the typical one-on-one Pinoy Henyo, only one representative from each group shall be asked to go to the front and have the mystery word card on his/her forehead. Only three words shall be allowed from the groups: “Oo”, “Hindi”, or “Pwede”. Violation of the rules of the game (e.g., communicating the mystery word to the guesser) shall merit corresponding penalties or disqualification. Assign three representatives per group to guess the mystery words. Each guesser shall be given one minute and 30 seconds. At the end of the activity, ask one or two learners what they think the learning objectives of the lesson will be. Immediately proceed with the Introduction.
Teacher tip For this particular lesson, start with the Motivation first (i.e., class activity on Pinoy Henyo Classroom Edition). After the game, proceed to the Introduction by communicating the learning objectives to the learners. For the part when the learners have to state the learning objectives using their own words, ask the learners to face their seatmates and work in pairs. If the learners are more comfortable in stating the learning objectives in Tagalog or In their local dialect, ask them to do so.
Teacher tip Prior to this lesson, assign a reading material or chapter for this topic. This shall aid in the facilitation of the class activity. In choosing the mystery words for the game, do not limit yourself with the four types of animal tissues. You may choose terms that describe the tissue type or even body parts wherein the tissues are located. You may also include diseases that are caused by certain malfunctions on the tissues. Make sure to mention the chosen mystery words in the discussion. This shall help the learners to understand the connection of the game with the lesson. Check how the class behaves during the activity. If the learners get rowdy, you may choose to stop the game. Make sure to warn the learners of the consequences first before the start of the activity.
INSTRUCTION/DELIVERY (95 MINS) Teacher tip Facilitate a five-minute review on the Hierarchy of Biological Organization and on the concept of “form fits function”, the unifying theme in Biology. Review on Hierarchy of Biological Organization
Do not use too much time for the review. Just make sure to guide or lead the learners in remembering past lessons. Provide clues if necessary.
1. Discuss that new properties arise with each step upward the hierarchy of life. These are called emergent properties. 2. Ask the class what the levels of biological organization are. The learners should be able to answer this since this is just a review. In case the class does not respond to the question, you may facilitate the discussion by mentioning the first level of the hierarchy. 3. Start with the cell since it is the most basic unit of life that shows all life properties. cells
tissue organ
organ system
multicellular organism
Illustrate this by showing photos of the actual hierarchy using animals that are endemic in the Philippines (e.g., pilandok, dugong, and cloud rat). Review on the unifying theme in Biology: “form fits function” 1. Ask the class what the relation of form (structure) to function and vice versa is 2. Ask for examples of versaingit of life that shows all life properthe torpedo shape of the body of dolphins (mammals with fishlike characteristics) and the bone structure and wing shape of birds in relation to flying.
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Teacher tip For the review on “form fits function”, if the class does not respond well, start giving your own examples for the students to figure out this unifying theme. Make sure to relate structure to function. Mention the role of fossils in determining the habits of extinct animals. By doing this, it shall establish a strong connection between form and function and shall give relevance on the study of this connection in Biology. After this, you may now proceed to the new topic on animal tissues.
Facilitate a class activity (i.e., observation of cells under a microscope) to illustrate that animals are made up of cells. This shall be the foundation of the definition of and discussion on animal tissues. The whole activity and discussion shall last for 90 minutes. If microscopes are available for this activity, set up the equipment and the slides that were prepared prior to the activity. Each slide should show one type of tissue (i.e., epithelial tissue, connective tissue, muscle tissue, and nervous tissue). Make sure that the labels are covered because the learners will be asked to name the tissues based on their observations during the discussion. If there are no microscopes available for the activity, prepare cut-out images, photos, or illustrations that show the different types of tissues (i.e., epithelial tissue, connective tissue, muscle tissue, and nervous tissue). Make sure that the images, photos, or illustrations are not labeled because the learners will be asked to name them. Also, do not immediately identify the type of tissue based on the descriptions that you will be presenting to the class. The learners will be asked to identify which among the slides under the microscope or which image, photo, or illustration matches the description of the structure and function that will be given during the discussion. After the class activity, proceed with the actual lecture. If a computer, laptop, or projector is available, show a PowerPoint presentation that shows the description and function of tissues. If there is no available equipment, you may use flash cards or manila paper where description of structure and function of the different tissue types are written down. Ask the learners which among the microscope slides, image, photo, or illustration fits the given information on description and function. After the learners’ responses, you can flash or show the next slide which shall reveal the image of the specimen with the corresponding label or type of tissue. Epithelial Tissue—This type of tissue is commonly seen outside the body as coverings or as linings of organs and cavities. Epithelial tissues are characterized by closely-joined cells with tight junctions (i.e., a type of cell modification). Being tightly packed, tight junctions serve as barriers for pathogens, mechanical injuries, and fluid loss.
Teacher tip If microscopes are available for this activity, allot 20-30 minutes for the observation of cells. If microscopes are not available, allot only 10-15 minutes. Prior to the activity, prepare the slides that will be put under the microscopes. The slides shall contain the different types of tissue. Make sure to focus the slides so that the learners can observe them clearly. Give the learners enough time to observe the specimens and then ask them to draw on their notebooks what they were able to observe under the microscopes. Encourage the learners to write down the description and function of the specific tissue type as you go through the discussion. If microscopes are not available and you have shown photos, images, or illustrations instead, ask the learners to draw them on their notebooks and encourage them to write down the description and function of the specific tissue type as you go through the discussion.
Teacher tip Prepare the lecture in such a way that you do not immediately reveal the label of the images or the terms that are being described. The learners should first be asked to identify the images or slides that fit the description of the structures and functions. This will make the students more engaged in the discussion. Always remind the learners to take down notes while you flash information for each tissue type.
Teacher tip Cells that make up epithelial tissues can have distinct arrangements: • • • • •
cuboidal—for secretion simple columnar—brick-shaped cells; for secretion and active absorption simple squamous—plate-like cells; for exchange of material through diffusion stratified squamous—multilayered and regenerates quickly; for protection pseudo-stratified columnar—single layer of cells; may just look stacked because of varying height; for lining of respiratory tract; usually lined with cilia (i.e., a type of cell modification that sweeps the mucus).
Figure 1: Epithelial Tissue (Source: Reece JB, U. L. (2010). Campbell Biology 10th. San Francisco (CA):.)
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Take note that the part on cell modifications is incorporated in the discussion on the structure of the respective cells that make up the tissue that is being discussed. Give emphasis on the differences on the features of the cells that make up the tissue type. For examples or illustrations of the different types of tissues, it is better to use an animal that is endemic in the Philippines or in your specific region so that the learners can relate more in the discussion.
Connective Tissue—These tissues are composed of the following: BLOOD —made up of plasma (i.e., liquid extracellular matrix); contains water, salts, and dissolved proteins; erythrocytes that carry oxygen (RBC), leukocytes for defense (WBC), and platelets for blood clotting. CONNECTIVE TISSUE PROPER (CTP)—made up of loose connective tissue that is found in the skin and fibrous connective tissue that is made up of collagenous fibers found in tendons and ligaments. Adipose tissues are also examples of loose connective tissues that store fats which functions to insulate the body and store energy. CARTILAGE —characterized by collagenous fibers embedded in chondroitin sulfate. Chondrocytes are the cells that secrete collagen and chondroitin sulfate. Cartilage functions as cushion between bones. BONE —mineralized connective tissue made by bone-forming cells called osteoblasts which deposit collagen. The matrix of collagen is combined with calcium, magnesium, and phosphate ions to make the bone hard. Blood vessesl and nerves are found at a central canal surrounded by concentric circles of osteons.
Figure 2: Connective Tissue (Source: Reece JB, U. L. (2010). Campbell Biology 10th. San Francisco (CA):.)
Muscle Tissue—These tissues are composed of long cells called muscle fibers that allow the body to move voluntary or involuntary. Movement of muscles is a response to signals coming from nerve cells. In vertebrates, these muscles can be categorized into the following: • skeletal—striated; voluntary movements • cardiac—striated with intercalated disk for synchronized heart contraction; involuntary • smooth—not striated; involuntary Figure 3: Muscle Tissue (Source: Reece JB, U. L. (2010). Campbell Biology 10th. San Francisco (CA):.) Nervous Tissue—These tissues are composed of nerve cells called neurons and glial cells that function as support cells. These neurons sense stimuli and transmit electrical signals throughout the animal body. Neurons connect to other neurons to send signals. The dendrite is the part of the neuron that receives impulses from other neurons while the axon is the part where the impulse is transmitted to other neurons. Figure 4: Neurons and Glial Cells (Source: Reece JB, U. L. (2010). Campbell Biology 10th. San Francisco (CA):.)
PRACTICE (60 MINS) Divide the class into six groups. Four groups will be reporting on Animal Tissues while two groups will be creating an infomercial on diseases caused by the malfunction of tissue types. Each infomercial group shall cover two tissue types. Each group will be given five minutes to report or show their infomercial. At the end of each presentation, facilitate a five-minute critiquing of the presentation. Make sure to get feedbacks from the learners and clarify misconceptions from the reports. The report or the infomercial on diseases shall not be graded. These will be a kind of formative assessment.Group the learners into pairs. Ask one to draw the mitochondria and label its parts while the other does the same for chloroplast. Once done, the partners exchange tasks (i.e., the learner that drew the mitochondria now does the same for the chloroplast).
EVALUATION (10 MINS)
Ask the learners to group themselves in pairs or in groups of threes. This will allow the learners to discuss and decide among themselves. However, if a learner chooses to do this activity on his or her own, he or she should be allowed to do so. Ask the learners to briefly and clearly answer the following questions: • • • • • •
What is the importance of having a tissue level in the hierarchy of biological organization? (2 points) What do the varying shapes and arrangement of epithelial tissue suggests? (2 points) What is the general function of connective tissues? What function is common to all types of connective tissues? (1 point) Why are there voluntary and involuntary muscle tissue functions? (2 points) What is the importance of glial cells in nervous tissues? (1 point) Identify two cell modifications and describe their respective functions. (2 points)
Teacher tip Group the learners before starting the lesson. The reporting may be done the day after finishing the discussion on Animal Tissue Structure, Function, and Cell Modification. The reports may be presented using a table which contains columns for tissue type, cell structures that characterize the tissue, part of the body where the tissue is located, function, and importance.
Teacher tip Assess if the learners are ready to answer this individually. If they are not yet ready, this activity can be done in pairs or in groups of threes. Make sure that you provide enough time for the group to discuss their responses. Remind the learners to answer briefly and clearly. If you are not comfortable with this time of exam, a multiple-choice type of evaluation may also be prepared. After getting the responses, you may get feedback from the learners to see if all members of each group helped or participated in their small discussions to answer the short quiz. You may ask learners to rate the members of their group.
General Biology 1
90 MINS
Cell Cycle and Cell Division Content Standard The learners demonstrate an understanding of the cell cycle and cell division (i.e., mitosis and meiosis).
LESSON OUTLINE Introduction Presentation of a simplified life cycle of a human being or plant
Motivation Performance Standards The learners shall be able to construct a three-dimensional model of the stages or phases involved in the cell cycle using indigenous or recyclable materials. Instruction/ The learners shall put emphasis on the identification of possible errors that may Delivery happen during these stages. Learning Competencies The learners: • • • • •
characterize the phases of the cell cycle and their control points (STEM_BIO11/12Id-f-6) describe the stages of mitosis and meiosis given 2n=6 (STEM_BIO11/12-Id-f-7) discuss crossing over and recombination in meiosis (STEM_BIO11/12-Id-f-8) explain the significance or applications of mitosis/meiosis (STEM_BIO11/12-Id-f-9) identify disorders and diseases that result from the malfunction of the cell during the cell cycle (STEM_BIO11/12-Id-f-10)
Specific Learning Outcomes • Identify and differentiate the phases of the cell cycle and their control points • describe and differentiate the stages of mitosis and meiosis given 2n=6 • discuss and demonstrate crossing over and recombination in meiosis • explain the significance and applications of mitosis and meiosis • construct a diagram of the various stages of mitosis and meiosis • identify disorders and diseases that result from malfunctions in the cell during the cell cycle
Practice
Video presentation of ‘Cell Cycle and Cell Division’
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Class activities or games such as Amazing Race or Interphase, Mitosis, or Meiosis Puzzle
10
and animal gametogenesis; Microscopic examination of an onion root tip Written or oral examination
5
5
Materials
photos of the life cycle or stages of eukaryotic organisms, yarns of different thickness, cords, beads, coins, pens Resources (continued at the end of Teaching Guide) (1) Becker, W.M. (2000). The World of the Cell. Addison Wesley Longman Inc., USA (2) Mader, S.S. (2011).Biology 10th Ed. Mac Graw Hill Education, USA.
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5
Lecture-discussion on the cell through the use of a PowerPoint presentation, video, or cell diagram on a Manila paper; Demonstration of the processes inside the cell using model materials (e.g., beads, cords, yarn with different thickness, coins, etc.); or, Summary of learners’ responses to questions regarding the video on ‘Cell Cycle and Cell Division’
Enrichment Video presentation or introduction on plant
Evaluation
5
INTRODUCTION (5 MINS)
Teacher tip
Introduce a simplified life cycle of a human being or plant. Let the learners identify the changes throughout the different stages and how these organisms grow and develop.
Explain to the learners that these eukaryotic organisms follow a complex sequence of events by which their cells grow and divide. This sequence of events is known as the Cell Cycle. You can show diagrams or illustrations that demonstrate the growth or increase in the number of organisms.
Figure 1: Life Cycle of Man and Higher Plants (Source: (n.d.). Retrieved from http:// www.vcbio.science.ru.nl/en/virtuallessons/cellcycle/postmeio/)
MOTIVATION (5 MINS) 1. Play the video on ‘Cell Cycle and Cell Division’. This video can be accessed at http:// www.youtube.com/watch?v=Q6ucKWIIFmg.Divide the class into two groups. 2. Show diagrams of cell division in multicellular or eukaryotic organisms to the class.
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Teacher tip You can download the video prior to this session or if internet connection is available during class, you can just make use of the hyperlink to play the video. To access the video through the hyperlink, simply hold the Control (Ctrl) Key on the keyboard and click on the hyperlink. You should ask the learners thoughtprovoking questions about the video and relate it to the lesson.
INSTRUCTION/DELIVERY (30 MINS)
Teacher tip
Facilitate a lecture-discussion on the general concepts of cell division. Cell Division—involves the distribution of identical genetic material or DNA to two daughter cells. What is most remarkable is the fidelity with which the DNA is passed along, without dilution or error, from one generation to the next. Cell Division functions in reproduction, growth, and repair. Core Concepts: • • • • • • • • • •
All organisms consist of cells and arise from preexisting cells. Mitosis is the process by which new cells are generated. Meiosis is the process by which gametes are generated for reproduction. The Cell Cycle represents all phases in the life of a cell. DNA replication (S phase) must precede mitosis so that all daughter cells receive the same complement of chromosomes as the parent cell. The gap phases separate mitosis from S phase. This is the time when molecular signals mediate the switch in cellular activity. Mitosis involves the separation of copied chromosomes into separate cells. Unregulated cell division can lead to cancer. Cell cycle checkpoints normally ensure that DNA replication and mitosis occur only when conditions are favorable and the process is working correctly. Mutations in genes that encode cell cycle proteins can lead to unregulated growth, resulting in tumor formation and ultimately invasion of cancerous cells to other organs.
The Cell Cycle control system is driven by a built-in clock that can be adjusted by external stimuli (i.e., chemical messages). Checkpoint—a critical control point in the Cell Cycle where ‘stop’ and ‘go-ahead’ signals can regulate the cell cycle. • •
Animal cells have built-in ‘stop’ signals that halt the cell cycles and checkpoints until overridden by ‘go-ahead’ signals. Three major checkpoints are found in the G1, G2, and M phases of the Cell Cycle. 38
Note the learners’ responses to questions about the video compared to the expected responses. The expected responses are the concepts listed in the Instruction / Delivery part.
The G1 Checkpoint—the Restriction Point • • • •
The G1 checkpoint ensures that the cell is large enough to divide and that enough nutrients are available to support the resulting daughter cells. If a cell receives a ‘go-ahead’ signal at the G1 checkpoint, it will usually continue with the Cell Cycle. If the cell does not receive the ‘go-ahead’ signal, it will exit the Cell Cycle and switch to a non-dividing state called G0. Most cells in the human body are in the G0 phase.
The G2 Checkpoint—ensures that DNA replication in S phase has been successfully completed. The Metaphase Checkpoint—ensures that all of the chromosomes are attached to the mitotic spindle by a kinetochore. Kinase—a protein which activates or deactivates another protein by phosphorylating them. Kinases give the ‘go-ahead’ signals at the G1 and G2 checkpoints. The kinases that drive these checkpoints must themselves be activated. • • • • • •
The activating molecule is a cyclin, a protein that derives its name from its cyclically fluctuating concentration in the cell. Because of this requirement, these kinases are called cyclin-dependent kinases or CDKs. Cyclins accumulate during the G1, S, and G2 phases of the Cell Cycle. By the G2 checkpoint, enough cyclin is available to form MPF complexes (aggregations of CDK and cyclin) which initiate mitosis. MPF functions by phosphorylating key proteins in the mitotic sequence. Later in mitosis, MPF switches itself off by initiating a process which leads to the destruction of cyclin. CDK, the non-cyclin part of MPF, persists in the cell as an inactive form until it associates with new cyclin molecules synthesized during the interphase of the next round of the Cell Cycle.
Discuss the stages of mitosis and meiosis. Mitosis (apparent division)—is nuclear division; the process by which the nucleus divides to produce two new nuclei. Mitosis results in two daughter cells that are genetically identical to each other and to the parental cell from which they came. Cytokinesis—is the division of the cytoplasm. Both mitosis and cytokinesis last for around one to two hours. Prophase—is the preparatory stage, During prophase, centrioles move toward opposite sides of the nucleus.
•
The initially indistinct chromosomes begin to condense into visible threads. • Chromosomes first become visible during early prophase as long, thin, and intertwined filaments but by late prophase, chromosomes are more compacted and can be clearly discerned as much shorter and rod-like structures. • As the chromosomes become more distinct, the nucleoli also become more distinct. By the end of prophase, the nucleoli become less distinct, often disappearing altogether.
Metaphase—is when chromosomes become arranged so that their centromeres become aligned in one place, halfway between the two spindle poles. The long axes of the chromosomes are 90 degrees to the spindle axis. The plane of alignment is called the metaphase plate. Anaphase—is initiated by the separation of sister chromatids at their junction point at the centromere. The daughter chromosomes then move toward the poles. Telophase—is when daughter chromosomes complete their migration to the poles. The two sets of progeny chromosomes are assembled into two-groups at opposite ends of the cell. The chromosomes uncoil and assume their extended form during interphase. A nuclear membrane then forms around each chromosome group and the spindle microtubules disappear. Soon, the nucleolus reforms. Meiosis—reduces the amount of genetic information. While mitosis in diploid cells produces daughter cells with a full diploid complement, meiosis produces haploid gametes or spores with only one set of chromosomes. During sexual reproduction, gametes combine in fertilization to reconstitute the diploid complement found in parental cells. The process involves two successive divisions of a diploid nucleus. First Meiotic Division The first meiotic division results in reducing the number of chromosomes (reduction division). In most cases, the division is accompanied by cytokinesis.
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Teacher tip You may show diagrams or a video demonstrating animal and plant mitosis. The video can be accessed at http:// www.vcbio.science.ru.nl/en/virtuallessons/ mitostage/
Prophase I—has been subdivided into five substages: leptonema, zygonema, pachynema, diplonema, and diakinesis. • • •
• •
Leptonema—Replicated chromosomes have coiled and are already visible. The number of chromosomes present is the same as the number in the diploid cell. Zygonema—Homologue chromosomes begin to pair and twist around each other in a highly specific manner. The pairing is called synapsis. And because the pair consists of four chromatids it is referred to as bivalent tetrad. Pachynema—Chromosomes become much shorter and thicker. A form of physical exchange between homologues takes place at specific regions. The process of physical exchange of a chromosome region is called crossing-over. Through the mechanism of crossing-over, the parts of the homologous chromosomes are recombined (genetic recombination). Diplonema—The two pairs of sister chromatids begin to separate from each other. It is at this point where crossing-over is shown to have taken place. The area of contact between two non-sister chromatids, called chiasma, become evident. Diakinesis—The four chromatids of each tetrad are even more condensed and the chiasma often terminalize or move down the chromatids to the ends. This delays the separation of homologous chromosomes.
In addition, the nucleoli disappear, and the nuclear membrane begins to break down. Metaphase I—The spindle apparatus is completely formed and the microtubules are attached to the centromere regions of the homologues. The synapsed tetrads are found aligned at the metaphase plate (the equatorial plane of the cell) instead of only replicated chromosomes. Anaphase I—Chromosomes in each tetrad separate and migrate toward the opposite poles. The sister chromatids (dyads) remain attached at their respective centromere regions. Telophase I—The dyads complete their migration to the poles. New nuclear membranes may form. In most species, cytokinesis follows, producing two daughter cells. Each has a nucleus containing only one set of chromosomes (haploid level) in a replicated form. Second Meiotic Division The events in the second meiotic division are quite similar to mitotic division. The difference lies, however, in the number of chromosomes that each daughter cell receives. While the original chromosome number is maintained in mitosis, the number is reduced to half in meiosis. Prophase II—The dyads contract. Metaphase II—The centromeres are directed to the equatorial plate and then divide. Anaphase II—The sister chromatids (monads) move away from each other and migrate to the opposite poles of the spindle fiber. Telophase II—The monads are at the poles, forming two groups of chromosomes. A nuclear membrane forms around each set of chromosomes and cytokinesis follows. The chromosomes uncoil and extend.
Cytokinesis—The telophase stage of mitosis is accompanied by cytokinesis. The two nuclei are compartmentalized into separate daughter cells and complete the mitotic cell division process. In animal cells, cytokinesis occurs by the formation of a constriction in the middle of the cell until two daughter cells are formed. The constriction is often called cleavage, or cell furrow. However, in most plant cells this constriction is not evident. Instead, a new cell membrane and cell wall are assembled between the two nuclei to form a cell plate. Each side of the cell plate is coated with a cell wall that eventually forms the two progeny cells. Meiosis
Teacher tip You can show a tabular comparison between mitosis and meiosis to point the significance of the two types of division. Divide the class into two groups and ask them about their opinions on the applications of mitosis and meiosis. The following could be possible responses:
Mitosis
1. Requires two nuclear divisions
1. Requires one nuclear division
2. Chromosomes synapse and cross over
2. Chromosomes do not synapse nor cross over
3. Centromeres survive Anaphase I
3. Centromeres dissolve in mitotic anaphase
4. Halves chromosome number
4. Preserves chromosome number
5. Produces four daughter nuclei
5. Produces two daughter nuclei
6. Produces daughter cells genetically different from parent and each other
6. Produces daughter cells genetically identical to parent and to each other
7. Used only for sexual reproduction
7. Used for asexual reproduction and growth
Table 1: Comparison of Mitosis and Meiosis (Source: http://courses.washington.edu/bot113/spring/ WebReadings/PdfReadings/TABLE_COMPARING_MITOSIS_AND.pdf) 42
Significance of mitosis for sexual reproduction: Mitosis is important for sexual reproduction indirectly. It allows the sexually reproducing organism to grow and develop from a single cell into a sexually mature individual. This allows organisms to continue to reproduce through the generations. Significance of Meiosis and Chromosome Number: Chromosomes are the cell's way of neatly arranging long strands of DNA. Non-sex cells have two sets of chromosomes, one set from each parent. Meiosis makes sex cells with only one set of chromosomes. For example, human cells have 46 chromosomes, with the exception of sperm and eggs, which contain only 23 chromosomes each. When a sperm cell fertilizes an egg, the 23 chromosomes from each sex cell combine to make a zygote, a new cell with 46 chromosomes. The zygote is the first cell in a new individual.
Meiosis I compared to Mitosis
Meiosis II compared to Mitosis
Meiosis I
Mitosis
Meiosis II
Mitosis
Prophase I
Prophase
Prophase II
Prophase
Pairing of homologous chromosomes
No pairing of chromosomes
No pairing of chromosomes
No pairing of chromosomes
Metaphase I
Metaphase
Metaphase II
Metaphase
Bivalents at metaphase plate
Duplicated chromosomes at metaphase plate
Haploid number of duplicated chromosomes at metaphase plate
Diploid number of duplicated chromosomes at metaphase plate
Anaphase I
Anaphase
Anaphase II
Anaphase
Homologues of each bivalent separate and duplicated chromosomes move to poles
Sister chromatids separate, becoming daughter chromosomes that move to the poles
Sister chromatids separate, becoming daughter chromosomes that move to the poles
Sister chromatids separate becoming daughter chromosomes that move to the poles
Telophase I
Telophase
Telophase II
Telophase
Two haploid daughter cells not identical to the parent cell
Two diploid daughter cells, identical to the parent cell
Four haploid daughter cells not genetically identical
Two diploid daughter cells, identical to the parent cell
Table 2: Meiosis compared to Mitosis Facilitate a discussion on disorders and diseases that result from the malfunction of the cell during the cell cycle. Present some diagrams or illustrations on some errors in mitosis and allow the learners to predict possible outcomes, diseases, or disorders that may happen: • •
incorrect DNA copy (e.g., cancer) chromosomes are attached to string-like spindles and begin to move to the middle of the cell (e.g., Down Syndrome, Alzheimer’s, and Leukemia)
Teacher tip Significance of Meiosis for Diversity: One of the benefits of sexual reproduction is the diversity it produces within a population. That variety is a direct product of meiosis. Every sex cell made from meiosis has a unique combination of chromosomes. This means that no two sperm or egg cells are genetically identical. Every fertilization event produces new combinations of traits. This is why siblings share DNA with parents and each other, but are not identical to one another.
Teacher tip You may show a video that demonstrates how crossing over and recombination of chromosomes occur. The video can be accessed at http:// highered.mheducation.com/sites/ 9834092339/student_view0/chapter11/ meiosis_with_crossing_over.html.s
Other chromosome abnormalities: • • • •
arise from errors in meiosis, usually meiosis I; occur more often during egg formation (90% of the time) than during sperm formation; become more frequent as a woman ages. Aneuploidy—is the gain or loss of whole chromosomes. It is the most common chromosome abnormality. It is caused by non-disjunction, the failure of chromosomes to correctly separate: • homologues during meiosis I or • sister chromatids during meiosis II
PRACTICE (10 MINS) Facilitate games like Amazing Race, Interphase/Mitosis/Meiosis Puzzle in the class. 1. The Amazing Race follows a series of stations or stages with challenges that the learners have to accomplish. Divide the class into groups after the discussion. The number of groups will depend on the number of stages or phases in the process (i.e., interphase, mitosis, or meiosis).
Teacher tip
2. The groups will race to accomplish the tasks in five stations. In each station, the learners will assemble given materials to illustrate stages or phases of events in the specific process (i.e., interphase, mitosis, or meiosis).
Encourage the learners to actively participate in the challenge. You may give extra points to those who will finish first.
ENRICHMENT (5 MINS)
A number of good videos have the stages or phases made into a rap or a song. One such example is the video entitled Cell Division Song Spongebob that can be accessed at http://www.youtube.com/watch? v=9nsRufogdoI. Encourage each group to brainstorm and point out their perceptions of the videos.
1. Instruct the learners to watch additional videos on cell division. 2. Introduce animal and plant gametogenesis to the learners in order for them to appreciate the significance of cell division. 3. Facilitate microscopic examination of onion root tip.
EVALUATION (5 MINS)
Facilitate the accomplishment of a self-assessment checklist.
A video on animal and plant gametogenesis can be accessed at http://csls-text.c.u-tokyo.ac.jp/active/ 12_05.html.
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ADDITIONAL RESOURCES: Books: 1. Raven, P. a. (2001). Biology 6th Ed. The McGraw Hill Company, USA 2. Reece, J. B. (2013). Campbell Biology, 10th Ed. Pearson Education, Inc. United States of America.
Electronic Resources: 3. (n.d.). Retrieved from Bright Hub Education: http://www.brighthubeducation.com/middle-school-science-lessons/94267-three-activities-forteaching-cell-cycles/# 4. (n.d.). Retrieved from http://www.uic.edu/classes/bios/bios100/lecturesf04am/lect16.htm 5. (n.d.). Retrieved from MH Education: http://highered.mheducation.com/sites/9834092339/student_view0/chapter11/ meiosis_with_crossing_over.html 6. (n.d.). Retrieved from http://www.vcbio.science.ru.nl/en/virtuallessons/meiostage/ 7. (n.d.). Retrieved from http://csls-text.c.u-tokyo.ac.jp/active/12_05.html 8. (n.d.). Retrieved from http://education.seattlepi.com/biological-significance-mitosis-meiosis-sexual-reproduction-5259.htm
General Biology 1
480 MINS
Transport Mechanisms Pt.1
LESSON OUTLINE
Content Standards The learners demonstrate an understanding of Transport Mechanisms:
Introduction Visualization of the plasma membrane and its
Simple Diffusion, Facilitated Transport, Active Transport, and Bulk/Vesicular Transport
Motivation
Simple group activity and brief reporting
Performance Standards The learners shall be able to construct a cell membrane model from indigenous Instruction/ Discussion and lecture proper Delivery or recyclable materials. Learning Competencies The learners: • • • •
Practice
describe the structural components of the cell membrane (STEM_BIO11/12–Ig-h-11) relate the structure and composition of the cell membrane to its function (STEM_BIO11/12-Ig-h-12) explain transport mechanisms in cells (diffusion, osmosis, facilitated transport, active transport) (STEM_BIO11/12–Ig-h-13) differentiate exocytosis and endocytosis (STEM_BIO11/12-Ig-h-14)
Specific Learning Outcomes At the end of the lesson, the learners shall be able to: • • • •
30
functions
60 120
45
Answering practice/guide questions
Enrichment Essay and concept map writing Evaluation
Designing a model of a plasma membrane using recyclable or indigenous materials
45 180
Materials
pen, paper, salt, water, recycled or indigenous materials
describe and compare diffusion, osmosis, facilitated transport and active transport explain factors that affect the rate of diffusion across a cell membrane predict the effects of hypertonic, isotonic, and hypotonic environments on osmosis in animal cells differentiate endocytosis (phagocytosis and pinocytosis) and exocytosis
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Resources
(1) Campbell, N. J. (n.d.). (2) Campbell, N. e. (2008). Biology 8th edition. Pearson International Edition. Pearson/Benjamin. (3) Freeman, S. (2011). Biological Science 4th edition International Edition. Benjamin Cummings Publishing. (4) Hickman, C. L. (2011). Integrated Principles of Zoology 15th edition. McGraw Hill Co., Inc.
INTRODUCTION (30 MINS)
1. Before this lesson, ask the learners to read about the topic on transport of materials across membranes. 2. Introduce the topic by providing the learners with background information.
In order for the cell to stay alive, it must meet the characteristics of life which include taking nutrients in and eliminating wastes and other by-products of metabolism. Several mechanisms allow cells to carry out these processes. All of the cell’s activities are in one way or another tied to the membrane that separates its interior from the environment. 3. Ask the learners how they understand and visualize a plasma membrane and what characteristics are essential for it to perform its function. 4. Ask the learners to identify the different mechanisms on how materials are transported in and out of the cell.
MOTIVATION (60 MINS)
1. Divide the learners into groups and ask them the following question: “What comes to your mind when you see a 20 year old man who is 7.5 ft. tall and 3.5 ft. tall man of the same age?” Among their respective groups, let the learners discuss the similarities and differences between the two. (Hint: Give students a clue by giving them the giant and pygmy as examples). 2. Ask a representative from each group to report the result of their discussion to the whole class. 3. Before the start of the lesson on diffusion, spray an air freshener in one corner of the room and ask the learners to raise their hands if they have smelled the scent of the spray. 4. Ask the learners what they have observed. Who smelled the scent first? Who are the last ones to smell the scent? How would you explain the phenomenon wherein learners in the same classroom smelled the spray at different times?
INSTRUCTION/DELIVERY (120 MINS)
1. Show an illustration of a plasma membrane to the learners. 2. Ask the learners to describe the plasma membrane. 3. Discuss the importance of the plasma membrane and how indispensable it is to the life of the cell. 4. Explain how plasma membranes are arranged in the presence of water. 5. Let the learners enumerate the structures found in a plasma membrane.
Teacher tip Different responses to the question will be drawn from students. Their responses will depend on what aspect they are looking into. Acknowledge the responses of the learners. Point out and explain that the two men are both abnormal. Their growths are abnormal such that one is too big in size and the other one is too small. Both men have defective membranes. Insufficient amount of growth hormones pass through a pygmy’s body while an excessive amount of growth hormones is released in a giant.
6. Explain to the learners the structure of a phospholipid bilayer.
Phospholipids are the foundation of all known biological membranes. The lipid bilayer forms as a result of the interaction between the nonpolar phospholipid tails, the polar phospholipid heads, and the surrounding water. The nonpolar tails face toward the water. Transmembrane proteins float within the bilayer and serve as channels through which various molecules can pass. 7. Ask the learners to enumerate the different transport mechanisms.
interior to accommodate the natural inward movement. Most plants are hypertonic with respect to their immediate environment. Osmotic pressure within the cell pushes the cytoplasm against the cell wall and makes a plant cell rigid.
8. Differentiate between diffusion and osmosis. 9. Compare and contrast facilitated diffusion and active transport.
10. Present photos of plant and animal cells immersed in an isotonic, hypotonic, and hypertonic solution.
To control the entrance and exit of particular molecules, selective transport of materials is necessary. One simple process is facilitated diffusion that utilizes protein transmembrane channels that are specific to certain molecules. It is a passive process driven by the concentration of molecules both inside and the outside of the membrane. Certain molecules are transported in and out of the cell, independent of concentration. This process requires the expenditure of energy in the form of ATP and is called active transport.
11. Describe solution and solute movement in and out of the cell under hypertonic, hypotonic, and isotonic conditions. 12. Explain the effects of the different solutions to the cells. Ask which among the three solutions is the best for plants? How about for animals? Explain to the learners the water requirement in plants.
Diffusion is the natural tendency for molecules to move constantly. Their movement is random and is due to the energy found in the individual molecules. Net diffusion occurs when the materials on one side of the membrane have a different concentration than the materials on the other side.
13. Differentiate among endocytosis, phagocytosis, pinocytosis, receptor-mediated endocytosis, and exocytosis.
Large molecules enter the cell by generalized nonselective process known as endocytosis. Phagocytosis is endocytosis of a particulate material while endocytosis of liquid material is called pinocytosis. Exocytosis is the reverse process. Receptormediated endocytosis is a complicated mechanism involving the transport of materials via coated vesicles.
Osmosis is a special type of diffusion specifically associated with the movement of water molecules. Many cells are isotonic to the environment to avoid excessive inward and outward movement of water. Other cells must constantly export water from their
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PRACTICE (45 MINS) Ask the learners to answer the following practice or guide questions: • • • •
What is the difference between diffusion and facilitated diffusion? How do endocytosis and exocytosis allow movement of materials in and out of the cell? What solution is best for a plant cell? How about for an animal cell? Explain the orientation of the phospholipid molecules in the presence of water.
ENRICHMENT (45 MINS)
Let the learners recognize the effect of a defective membrane in normal body functioning. Ask them to write an essay about the possible effects of a faulty plasma membrane aside from the examples given earlier. Ask the learners to individually submit a concept map about plasma membrane and the different transport mechanisms.
EVALUATION (180 MINS)
Ask the learners to design and a model of a plasma membrane using recyclable or indigenous materials. Divide the learners into groups and assign different concentrations of salt solution to be used in making salted eggs. Ask the learners to answer the following questions: • •
Why does putting salt on meat preserve it from bacterial spoilage? Compare specific transport processes (i.e., diffusion, osmosis, facilitated transport, active transport, endocytosis, and exocytosis) in terms of the following: • concentration gradient • use of channel or carrier protein • use of energy • types or sizes of molecules transported
General Biology 1
240 MINS
Transport Mechanisms Pt.2
LESSON OUTLINE
Content Standard Introduction Presentation of objectives and important terms; Discussion on the structure of the plasma The learners shall be able to construct a cell membrane model from indigenous membrane; Brief discussion on the different or recyclable materials.
15
transport mechanisms
Performance Standard The learners shall be able to construct a cell membrane model from indigenous Motivation or recyclable materials. Learning Competencies The learners: • • • •
describe the structural components of the cell membrane (STEM_BIO11/12–Ig-h-11) relate the structure and composition of the cell membrane to its function (STEM_BIO11/12-Ig-h-12) explain transport mechanisms in cells (diffusion, osmosis, facilitated transport, active transport) (STEM_BIO11/12–Ig-h-13) differentiate exocytosis and endocytosis (STEM_BIO11/12-Ig-h-14)
Specific Learning Outcomes At the end of the lesson, the learners shall be able to: • • • • • • •
describe the plasma membrane explain how plasma membranes are arranged in the presence of water understand the structure of the phospholipid bilayer describe and compare diffusion, osmosis, facilitated transport and active transport explain factors that affect the rate of diffusion across a cell membrane predict the effects of hypertonic, isotonic, and hypotonic environments on osmosis in animal cells differentiate endocytosis (phagocytosis and pinocytosis) and exocytosis
Class activity to illustrate the process of diffusion; Discussion of similarities between a giant and pygmy; Demonstration of the principle behind the process of making salted eggs
15
Instruction/ Delivery
Discussions, as a class and among groups, on the structure and importance of the plasma membrane and on the different transport mechanisms
60
Practice
Answering of practice or guide questions
30
Enrichment
Essay writing or concept mapping; Class activity on salted egg making
60
Evaluation
Construction of a plasma membrane model from indigenous or recyclable materials; Concept mapping on the different transport mechanisms; Answering of questions for assessment
60
Materials projector, laptop (if available), visual aids, school supplies, recycled or indigenous materials Resources (1) Campbell, N.A. et. al. (2008). Biology 8th Edition Pearson International. Pearson/Benjamin Cummings Publishing. (2) Campbell, N. J. (2010). Biology 9th edition Pearson International Edition. Benjamin Cummings Publishing. (3) Freeman, S. (2011). Biological Science. 4th edition. International Edition. Benjamin Cummings Publishing. (4) Hickman, C. L. (2011). Integrated Principles of Zoology. 15th edition. McGraw Hill Co., Inc.
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INTRODUCTION (15 MINS)
Teacher tip
Prior to this lesson, instruct the learners to read up on the transport of materials across membranes. Ask the learners to identify the different mechanisms on how materials are transported in and out of the cell. Introduce the topic by providing the learners with background information.
After the learners have enumerated the different transport mechanisms, ask them why they think there is a need to have different kinds of processes that allow materials to be transported in and out of the cell.
In order for the cell to stay alive, it must meet the characteristics of life which include taking nutrients in and eliminating wastes and other by-products of metabolism. Several mechanisms allow cells to carry out these processes. All of the cell’s activities are, in one way or another, tied to the membrane that separates its interior from the environment. Ask the learners how they visualize a plasma membrane and what characteristics do they think are essential for it to perform its function.
Learners will describe the plasma membrane in different ways. Ask them how they think the structures found within the membrane help in performing its function and what might happen in the absence of the these structures
Teacher tip
MOTIVATION (15 MINS)
Allow some time for the learners to smell the spray until everyone has already smelled the scent. Remember to instruct the learners to raise their hand once they smell the scent.
Before the start of the lesson on diffusion, conduct this simple class activity. Spray an air freshener in one corner of the room and instruct the learners to raise their hands if they have smelled the scent of the spray. Ask the learners the following questions: • Who among the class were able to smell the air freshener first? • Who among the class were the last ones to smell the air freshener? • How would you explain the phenomenon wherein people in the same classroom smelled the scent of the air freshener at different times? Divide the learners into groups and ask them the question: What comes to your mind when you see two men who are of the same age but one is 7.5 feet tall and the other is 3.5 feet tall? Allow the learners to discuss the similarities and differences between the two among their groups. Ask a representative from each group to present the results of their discussions to the whole class.
The learners might give varying responses to the question depending on what aspect they are looking into. Give hints by providing the giant and pygmy as examples. Acknowledge the learners’ responses and point out that the two men are similar in the sense that they are both abnormal. Growth in both men is abnormal such that one is too big in size while the other one is too small. Explain that both men have abnormal growth. Both have defective membranes. Insufficient amount of growth hormones pass through a pygmy’s body while an excessive amount of growth hormones is released in a giant.
INSTRUCTION/DELIVERY (60 MINS)
Teacher tip
Structure, function and importance of the plasma membrane 1. Present an illustration of the plasma membrane to the class 2. Ask the learners to describe the plasma membrane. 3. Discuss the importance of the plasma membrane and how indispensable it is to the life of the cell. 4. Explain how plasma membranes are arranged in the presence of water. 5. Let students enumerate structures found in a plasma membrane. 6. Make students understand the structure of a phospholipid bilayer. Plasma membranes—are made up of a phospholipid bilayer in an aqueous environment. Phospholipids are the foundation of all known biological membranes. The lipid bilayer forms as a result of the interaction between the non-polar (hydrophobic or water-fearing) phospholipid tails, the polar (hydrophilic or water-loving) phospholipid heads, and the surrounding water. The nonpolar tails face toward the water. Transmembrane proteins float within the bilayer and serve as channels through which various molecules can pass. They function as ‘identification tags’ on cells which enable the cell to determine if the other cells that it encounters are like itself or not. It also permits cells of the immune system to accept and reject foreign cells such as disease-causing bacteria. Many membrane proteins function as enzymes that speed up reactions in cells. Others act like paste or glue-forming cell junctions where adjacent cells stick together. Membranes also contain cholesterol which reduces the cell’s permeability to substances and make the bilayer stronger. Transport Mechanisms 1. Ask the learners to enumerate the different transport mechanisms. 2. Differentiate between diffusion and osmosis.
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You can ask the following questions before starting the discussion: Have you realized how crucial the task of a plasma membrane is in maintaining the life of a cell? Have you thought about the ways on how the materials needed by the cell and the wastes it needs to dispose are able to move in and out of the plasma membrane?
Molecules and substances move in several ways that fall within two categories: passive transport and active transport. In passive transport, heat energy of the cellular environment provides all of the energy, hence, this is not energy-costly to the cell. Active transport, however, requires the cell to do work, requiring the cell to expend its energy reserves. Diffusion is a type of passive transport described as the natural tendency for molecules to move constantly. Their movement is random and is due to the energy found in the individual molecules. Net diffusion occurs when the materials on one side of the membrane have a different concentration than the materials on the other side. Osmosis is a special type of diffusion specifically associated with the movement of water molecules. A solution with a higher concentration of solutes is said to be hypertonic while a solution with a lower concentration of solutes is hypotonic. Water crosses the membrane until the solute concentrations are equal on both sides. Solutions of equal solution concentration are said to be isotonic. This only occurs when the solute concentration are the same on both sides of the membrane. Compare and contrast facilitated diffusion and active transport. Then present photos of plant and animal cells immersed in an isotonic, hypotonic, and hypertonic solution. In addition, describe a solution and solute movement into and out of the cell under hypertonic, hypotonic and isotonic conditions. Explain the effects of the different solutions to the cells. Ask which among the three solutions is the best for plants? For animals? Let them understand water requirement in plants. Many cells are isotonic to the environment in order to avoid excessive inward and outward movement of water. Other cells must constantly export water from their interior to accommodate the natural inward movement. Most plants are hypertonic with respect to their immediate environment. Osmotic pressure within the cell pushes the cytoplasm against the cell wall and makes a plant cell rigid. Ask the learners the following questions: • • •
How do cells behave in different solutions? What do you notice about the effect of different solutions to animal and plant cells? What solution is best for an animal cell? Does this hold true with plant cells?
When an animal cell such as red blood cell is immersed in an isotonic solution, the cell gains water at the same rate that it loses it. The cell’s volume remains constant in this situation.
What will happen to the red blood cell when immersed in a hypotonic solution which has a lower solute concentration than the cell? The cell gains water, swells, and may eventually burst due to excessive water intake. When placed in a hypertonic solution, an animal cell shrinks and can die due to water loss. Water requirement for plant cells is different due to their rigid cell walls. A plant cell placed in an isotonic solution is flaccid and a plant wilts in this condition. In contrast with animal cells, a plant cell is turgid and healthy in a hypotonic solution. In a hypertonic solution, a plant cell loses water, shrivels, and its plasma membrane detaches from the cell wall. This situation eventually causes death in plant cells. Differentiate diffusion from facilitated diffusion. To control the entrance and exit of particular molecules, selective transport of materials is necessary. One simple process is facilitated diffusion that utilizes protein transmembrane channels that are specific to certain molecules. It is a passive process driven by the concentration of molecules on the inside and the outside of the membrane. Certain molecules are transported in and out of the cell, independent of concentration. This process requires the expenditure of energy in the form of ATP and is called active transport.
Differentiate endocytosis, phagocytosis, pinocytosis, receptor-mediated endocytosis, and exocytosis.
Large molecules enter the cell by generalized non-selective process known as endocytosis. Phagocytosis is endocytosis of a particulate material while pinocytosis is endocytosis of liquid material. In this process, the plasma membrane engulfs the particle or fluid droplet and pinches off a membranous sac or vesicle with a particular fluid inside into the cytoplasm. Exocytosis is the reverse process where a membrane-bound vesicle filled with bulky materials moves to the plasma membrane and fuses with it. In this process, the vehicle’s contents are released out of the cell. Receptor-mediated endocytosis is a complicated mechanism involving the transport of materials through coated vesicles. Cells take up molecules more efficiently in this process due to the receptor proteins on their surfaces. Each receptor protein bears a binding site for a particular molecule. If the right molecule contacts a receptor protein, it attaches to the binding site, forming a pocket and eventually pinching off into the cytoplasm.
PRACTICE (30 MINS)
Ask the learners to answer the following questions: • •
Explain the orientation of the phospholipid molecules in the presence of water. Enumerate the structures found in a plasma membrane and give the function of each.
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• • • • • •
How do diffusion and facilitated diffusion differ? How do endocytosis and exocytosis allow movement of materials in and out of the cell? What solution is best for a plant cell? How about for an animal cell? Give two ways by which one could determine whether active transport is going on. Compare and contrast the effects of hypertonic and hypotonic solutions on plant and animal cells. What role do vacuoles play in endocytosis and exocytosis?
ENRICHMENT (60 MINS) Essay writing and concept mapping 1. Ask the learners to write an essay about the possible effects of a faulty plasma membrane aside from the examples given in the lesson. Let the learners recognize the effects of a defective membrane to normal bodily functions. 2. Ask the learners to individually submit a concept map about the plasma membrane. You can provide them with sample words for their concept map: • • • • • • •
plasma membrane semipermeable phospholipid bilayer hydrophilic heads hydrophobic tails cholesterol membrane proteins
Teacher tip For the concept mapping, you can provide the learners with key words or allow them to come up with their own key words for their concept map.
Creating own saturated salt solution for salted egg-making 1. Divide the class into groups and assign different concentrations of salt solutions to be used in making salted eggs. 2. Instruct the learners to make their own salt solutions and take note of the concentration that they opt to use.
Teacher tip Diffusion and osmosis are two processes involved in making salted eggs. The salt solution should be supersaturated in order to produce good and delicious salted eggs.
EVALUATION (60 MINS) Building of plasma membrane model 1. Divide the class into groups. 2. Ask the groups to design and build a model of a plasma membrane using recyclable or indigenous materials. Concept mapping Ask the learners to individually submit a concept map about the different transport mechanisms. You can provide them with sample words for their concept map or allow them to come up with their own:
• plasma membrane • phagocytosis • transport mechanisms • pinocytosis • passive transport • receptor-mediated endocytosis • active transport • diffusion • hypotonic • facilitated diffusion • hypertonic • endocytosis • isotonic
• exocytosis Assessment questions: Instruct the learners to answer the following questions to assess their knowledge and understanding of the lesson: • •
Why does putting salt on meat preserve it from spoilage by bacteria? Compare specific transport processes (i.e., diffusion, osmosis, facilitated transport, active transport, endocytosis, and exocytosis) in terms of the following: • concentration gradient • use of channel or carrier protein • use of energy • types or sizes of molecules transported
56
Teacher tip You can provide the learners with key words or allow them to come up with their own key words for their concept map.
General Biology 1
Carbohydrates and Lipids: Structures and Functions of Biological Molecules Content Standard The learners demonstrate an understanding of the structures and functions of carbohydrates and lipids and their roles in specific metabolic processes. Performance Standard The learners shall be able to explain the role and significance of carbohydrates and lipids in biological systems. Learning Competencies The learners: • • •
categorize the biological molecule as a carbohydrate or lipid according to their structure and function (STEM_BIO11/12-Ii-j-15) explain the role of each biological molecule in specific metabolic processes (STEM_BIO11/12-Ii-j-16) detect the presence of carbohydrates and lipids in food products using simple tests
Specific Learning Outcomes At the end of the lesson, the learners shall be able to: • •
120 MINS
LESSON OUTLINE Introduction Presentation of learning objectives and important terms; Discussion on dehydration reactions and hydrolysis
Motivation
10
Relating the lessons to real-life situations; Discussion on food as sources of energy and building blocks
10
Instruction/ Discussion, as a class and among groups, on Delivery/ the structure and importance of Practice carbohydrates and lipids.
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Enrichment Laboratory activity on testing the
20
Evaluation
20
presence of carbohydrates and lipids on common food products Group activity on making molecular models of carbohydrates and lipids
Materials
projector, laptop (if available), sample food labels, common food or drink products (e.g. flour, cornstarch, cooking oil, present simple molecular models of carbohydrates and lipids and relate the food or drink brought by the learners structure to the roles that these molecules play in biological systems perform tests for the presence of starch and reducing sugars and lipids on Resources common food products (1) Reece, J.U. (2011). Campbell Biology, 9th ed. San Francisco, CA: Pearson Benjamin Cummings
INTRODUCTION (10 MINS)
Teacher tip
Communicate learning objectives and important terms
Prominently display the learning objectives and important terms on one side of the classroom and frequently refer to them during the discussion. You may place a check-mark beside a term in the wordlist after defining it so that the learners have an idea of their progress.
Introduce the following learning objectives using any of the suggested protocols (i.e., verbatim, own words, or read-aloud) • • •
I can distinguish a carbohydrate from a lipid given its chemical structure and function. I can explain the roles played by carbohydrates and lipids in biological systems. I can detect the presence of carbohydrates and lipids in food products using simple chemical tests.
Introduce the list of important terms that learners will encounter in this lesson:
• macromolecule • cellulose • polymer • chitin • monomer • lipids • dehydration reaction • fat • hydrolysis • fatty acid • carbohydrates • triacylglycerol • monosaccharides • saturated fatty acid • disaccharides • unsaturated fatty acid • glycosidic linkage • trans fat • polysaccharide • phospholipids • starch • steroids • glycogen • cholesterol
MOTIVATION (10 MINS)
1. Divide the class into groups of three. 2. Distribute sample food or nutrition labels to each group and ask them if they know how to interpret the information written on the food labels.
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Each learner can also illustrate or define the term on a sheet of paper which can be tacked beside the list of words. Another way of incorporating lists of important terms is to have the words placed in a blank bingo card grid. Learners can write a short definition or description of the term under the entry in the bingo card to block out a square. This may serve as the learners’ reference guide or method of formative assessment.
You may ask the following questions to facilitate the discussion and call on several groups to present in front of the class: •How many servings are in this container? •Would you agree that this is the reasonable amount of food you would consume per serving? How many total food calories (C) are in this container? •How much fat is present in one serving? What kind of fat? What is the importance of consuming fats in our diet? •How much carbohydrates are present in one serving? What kind of carbohydrates? What is the importance of consuming carbohydrates in our diet? •Decide on whether this food sample can be eaten often or sparingly and justify.
3.Recall that human beings, like all animals, are heterotrophs that need to take in energy and organic molecules (carbohydrates, fats, and proteins) from plant and animal matter. 4.Explain to the learners that this lesson will describe the structure of carbohydrates and lipids and explain the role that these biomolecules play in important biological processes.
Teacher tip For the food labels, local products that are familiar to the learners will make the best samples. Make sure that the labels have carbohydrates, fats, and fibers in them. If there are no food labels available, you may do an image search and print some sample food labels from the internet. Division into small groups of two or three may facilitate sharing. Only call on two or three groups to present if there is limited time. Expect the responses to vary depending on how realistic the serving sizes are. You can also discuss about how advertisers can influence how people perceive food. Take note that a food calorie is the same as 1 kcal or 1000 calories. A young adult would often need to take 1800-2500C per day depending on their size and level of activity.
Responses may include saturated, unsaturated, and trans fats. Explain to the learners that these fats will be discussed in more detail during the lesson. Regarding its importance, expect responses ranging from energy source, insulation, for flavor, for aid in cooking, for heart health, skin health, etc. Possible responses include sugar, fibers, etc. Regarding its importance, responses may include energy source, for aid in regular bowel movement, for provision of building blocks for biosynthesis, etc.
INSTRUCTION/DELIVERY (60 MINS) Present a diagram similar to the one below.
Table 1: Abundant elements in the human body (Source: http://www.personal.psu.edu/staff/m/b/ mbt102/bisci4online/chemistry/elementsorgnsm.jpg) Point out that the bulk (i.e., more than 90%) of the human body weight is provided by only three elements: oxygen, carbon, and hydrogen. We get these elements primarily from the food we eat, from the water we drink, and from the air we inhale around us. Explain to the learners that biogeochemical cycles such as the carbon-oxygen cycle and the water cycle play important roles in ensuring that we have access to these important elements. All forms of life, not only that of humans, are made up of four kinds of important large molecules: carbohydrates, lipids,
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proteins, and nucleic acids. All of these have carbon atoms as their backbones since carbon is capable of forming up to four chemical bonds with atoms of other elements. Facilitate the lecture on carbohydrates and lipids. What do humans get from food? Heterotrophs, such as human beings, obtain energy and raw materials from food. These are important for cell growth, cell division, metabolism, repair, and maintenance of the body. Nutrients can be classified as either organic nutrients (i.e., those that contain carbon such as carbohydrates, fats, proteins, vitamins, and nucleic acids) or inorganic nutrients (i.e., those that do not contain carbon such as water and mineral salts). What are carbohydrates? Carbohydrates are organic compounds made up of carbon, hydrogen, and oxygen. These compounds have a general formula of CnH2mOm. This means that the hydrogen and oxygen atoms are present in a ratio of 2:1. For example, glucose has a formula of C6H12O6 and sucrose has a formula of C12H22O11. Carbohydrates are usually good sources of raw materials for other organic molecules and energy. One gram of carbohydrates provides four food calories or 16 kJ of energy. In the human diet, carbohydrates mainly come from plants although they are found in all organisms. How are carbohydrates formed? Carbohydrates are examples of macromolecules. These are chainlike molecules called polymers (mere means part) made from repeating units like monomers. Polymers can be formed from covalently-bonded monomers much like a single structure can be made out of repeated building blocks linked to each other. These monomers, called monosaccharides, form covalent bonds when one monomer loses a hydroxyl group and the other loses a hydrogen atom in dehydration or condensation reactions, forming disaccharides. This reaction requires energy to occur. The bond formed is called a glycosidic linkage.
Teacher tip
Figure 2: Dehydration synthesis of disaccharides from monosaccharide components (Source: https:// bealbio.wikispaces.com/file/view/disaccharides.JPG/364413582/disaccharides.JPG) Longer polysaccharide chains are formed by monomer addition through succeeding dehydration reactions. These reactions can occur in the human liver as carbohydrates are stored as polysaccharides called glycogen or in ground tissues of plants where these are stored as starch. Polysaccharides are broken down into simpler components through the use of water to break covalent bonds and release energy. The process, known as hydrolysis (hydro means water and lysis means split), is the opposite of dehydration reactions and often occurs in the digestive tract during chemical and mechanical digestion. Here, enzymes break bonds within polysaccharides. With the aid of water, one – H group attaches to a monosaccharide while another –OH group attaches to the other. Comprehension question: How many molecules of water are needed to completely hydrolyze a polysaccharide that is one thousand monosaccharides long?
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Use ball and stick models or plastic blocks to demonstrate how dehydration and hydrolysis reactions occur. Simple reusable ones may be constructed from toothpicks or clay or similar materials.
If a projector is available, you may also use animations like the ones found at to help in visualization. Correct response: 999 water molecules During the discussion, invite the learners to find different kinds of carbohydrates in their food labels.
How are carbohydrates classified? Carbohydrates can be classified into three main categories, according to increasing complexity: •
monosaccharides (monos means single and sacchar means sugar)
• •
disaccharides (di means two) polysaccharides (poly means many)
Some notes on their structures and functions are found in the following table: Classification
Monosaccharide
Functions
• •
major cellular nutrient often incorporated into more complex carbohydrates
Structure
•
• •
contains a carbonyl group • (C=O) and may be classified as an aldose or ketose depending on the • position may have three to seven carbons in the skeleton may be arranged in a linear form when solid and is converted into a • ring form in aqueous solution (α form when H is on top of plane of ring and β form when -OH is on top of plane of ring)
Examples
Ribose—a 5C aldose that forms part of the backbone of nucleic acids Glucose—a 6C aldose that is the product of photosynthesis and the substrate for respiration that provides energy for cellular activities Fructose—a 6C ketose that is found in many plants and is often bonded to glucose
Classification Disaccharide
Functions
• •
energy source sweetener and dietary component
Structure
•
forms when a glycosidic linkage forms between two monosaccharides
Examples •
•
•
Polysaccharide
• storage material for important monosaccharides • structural material for the cell or the entire organism
• forms when hundreds to thousands of monosaccharides are joined by glycosidic linkages
•
•
Maltose (glucose + glucose)—malt sugar often found in sprouting grains, malt-based energy drinks, or beer Lactose (glucose + galactose)—milk sugar that is a source of energy for infants; an enzyme called lactase is required to digest this. Many adult Filipinos have low levels of this enzyme leading to a condition called lactose intolerance. Sucrose (glucose + fructose)—found in table sugar processed from sugar cane, sweet fruits, and storage roots like carrots Storage polysaccharides are large molecules retained in the cell and are insoluble in water (formed from α 1,4 linkage monomers; with a helical structure)
o Starch—amylase is unbranched starch forming a helical structure while amylopectin is branched starch, these are present in plant parts like potato tubers, corn, and rice and serve as major sources of energy.
o Glycogen—found in animals and fungi; often found in liver cells and muscle cells Structural polysaccharides (formed from β 1,4 linkage of monomers; strands associate to form a sheet-like structure)
o Cellulose—tough sheet-like structures that make up plant and algal cell walls that may be processed to form paper and paper-based products; humans lack the enzymes to digest β 1,4 linkages so is passed out of the digestive tract and aids in regular bowel movement
o Chitin—used for structural support in the walls of fungi and in external skeletons of arthropods
o Peptidoglycan—used for structural support in bacterial cell walls
Teacher tip Examples of alpha helices and beta sheets may be created using wire for the backbone and yarn for the Hbonds; invite learners to speculate on why alpha helix structures are associated with storage polysaccharides and beta sheets with structural polysaccharides.
Teacher tip Invite learners to compare the rigidity or structural integrity of plant matter or paper, a shrimp’s shell, and a mushroom. Explain that all these structures are formed from β sheets.
What are lipids?
Teacher tip
Lipids are a class of large biomolecules that are not formed through polymerization. They have diverse structures but are all non-polar and mix poorly, if at all, with water. They may have some oxygen atoms in their structure but the bulk is composed of abundant nonpolar C-H bonds. They function for energy storage, providing nine food calories or 37 kJ of energy per gram. They also function for the cushioning of vital organs and for insulation. Furthermore, they play important roles in plasma membrane structure and serve as precursors for important reproductive hormones.
Fats or triacylglycerol formation may be explained better using a diagram such as the one below or through models patterned after a similar diagram. You may ask the learners to explain, in their own words, what they think is happening and compare the formation of carbohydrates with that of lipids.
How are lipids classified? Lipids can be divided into three main classes according to differences in structure and function. Some notes on their structures and functions are found in the following table:
Classification
Functions
Fats (triacylglycerols or triglycerides)
• energy storage • cushioning of vital organs (adipose tissue) • insulation
Structure •
•
formed from dehydration reactions between glycerol (an alcohol with three Cs, each with an –OH group) forming three ester linkages with three fatty acids (16-18 Cs, with the last C as part of a –COOH group) and producing three molecules of water component fatty acids (FA) may be either saturated or unsaturated
o Saturated FA (e.g., palmitic acid) have the maximum number of hydrogen atoms bonded to each carbon (saturated with hydrogen); there are no double bonds between carbon atoms
o Unsaturated FA (e.g., oleic acid) have at least one double bond, H atoms are arranged around the double bond in a cis configuration (same side) resulting in a bend in the structure
Teacher tip
Demonstrate the effects of the straight chains of saturated FAs on packing by piling together flat structures like books or blackboard erasers and ask learners to Examples compare this with the stacking or packing of • Saturated fat—animal products such as irregularly shaped objects like partiallybutter and lard have a lot of saturated fatty acids. folded sheets of cardboard. The linear structure allows for the close packing of the fat molecules for ming solids at room temperature, diets high in these fats may increase the risk of developing atherosclerosis, a condition in which fatty deposits develop within the walls of blood vessels, increasing the incidence of cardiovascular disease • Unsaturated fat—plant and fish oils have unsaturated fatty acids. The bent structure prevents close packing and results in oils or fats that are liquid at room temperature. Homemade peanut butter has oils that separate out of solution for this reason. Industries have developed a process called hydrogenation that converts unsaturated fats into saturated fats to improve texture spreadability. • Trans fat—may be produced artificially through the process of hydrogenation described above. The cis double bonds are converted to trans double bonds (H atoms on opposite sides) resulting in fats that behave like saturated fats. Studies show that trans fat are even more dangerous to health than saturated fats to the extent that they have been banned from restaurants in some countries.
During discussion, invite the learners to find different kinds of fats in their food labels and decide on whether a particular food is healthier than another based on its fat content.
Misconception Clarify the misconception that consuming fats is entirely dangerous for health. Fats are an essential part of a healthy diet when consumed in moderation.
Classification Phospholipids
Functions major component of cell membranes
•
•
Structure formed from dehydration reactions between glycerol (an alcohol with three Cs, each with a –OH group), forming two ester linkages with two fatty acids (16-18 Cs, with the last C as part of a –COOH group) and a last linkage with a phosphate group
Examples Phospholipids self-assemble into bilayers when surrounded by water and form the characteristic structure of plasma membranes
Steroid structure may be explained better using a diagram such as the one below or through models patterned after a similar diagram. You may ask the learners to describe the diagram in their own words and compare the structure of cholesterol with that of other lipids.
•
Steroids and sterols
• regulate fluidity of cell membranes • base of sex hormones • emulsification of fats during digestion
• functional group attached to the rings vary (if – OH is attached to the 4th C, then it is called a cholesterol)
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Phospholipid structure may be explained better using a diagram such as the one below or through models patterned after a similar diagram. You may ask the learners to describe the diagram in their own words and compare the structure of fats with that of phospholipids.
Teacher tip
phosphate group is hydrophilic and is called the ‘head’ of the molecule
fatty acids are hydrophobic and form the ‘tails’ of the molecule • characterized by a Cskeleton with four fused rings
Teacher tip
• Cholesterol found in cell membranes regulates the rigidity of the cell membrane and are the base material for the production of sex hormones like estradiol and progesterone
ENRICHMENT (20 MINS)
Divide the class into groups. Instruct the learners to prepare the following materials that are needed for the laboratory activity:
• eight glass droppers, medicine droppers, or caps • ethanol solution • 12 test tubes • glucose solution • test tube holders or tongs • flour or cornstarch • beaker • cooking oil • alcohol lamp • sample of studentbrought food or drink • Benedict’s solution • iodine solution • mortar and pestle
Explain the following processes to the learners. Benedict’s solution, a blue solution with CuSO4(aq), can detect the presence of reducing sugars (i.e., any sugar with a free aldehyde or ketone group such as all monosaccharides and the disaccharides lactose and maltose). When boiled, these sugars reduce Cu2+ in Benedict’s solution to produce a brickred precipitate of Cu2O(s).
Iodine test can be used to detect the presence of starch.
Teacher tip This activity may be done as a class if time does not permit for the activity to be done in separate groups. If Benedict’s solution is not available, you may only perform the last two tests. In the absence of laboratory grade chemicals, you may improvise with storebought chemicals like iodine and 70% ethyl alcohol for medical use. Make sure to test the procedure before performing the activity in the class.
Emulsion test can be used to identify fats.
Learners should perform all three tests on the following samples:
• glucose solution (available in the baking section of grocery stores)
•
cooking oil
food or drink sample that the learners • flour or cornstarch solution brought.
For solid samples, instruct the learners to mash a small portion of the sample in some water using the mortar and pestle and then test the resulting solution. Ask the learners to prepare a table with appropriate headings in which to record their results. •
In discussing the results, ask the learners to conclude whether carbohydrates or lipids are present in their samples. They may compare this with the list of ingredients for their food or drink sample. They can also list possible sources of errors.
EVALUATION (20 MINS)
Divide the class into small groups. Provide the groups with different structures of lipids or carbohydrates and ask them to create models using common or recyclable materials. Ask the learners to explain or write a short description of their models. In grading the models, check to see if the learners were able to create an accurate model of the assigned lipid or carbohydrate. Ask the learners, still in their small groups, to create a short flowchart that will allow them to distinguish between the different kinds of carbohydrates and lipids based on their structures. They may use this flowchart in answering the comprehension questions that follow. Provide different molecular structures of the following and ask the learners to identify whether these are:
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Teacher tip Prior to this lesson, instruct the learners to bring recyclable materials that they can use for this activity.
• •
monosaccharides
disaccharides
•
unsaturated fats
•
storage polysaccharides
•
phospholipids
•
structural polysaccharides
•
steroids.
• saturated fats You may also ask the learners to give one of the associated functions or characteristics of the given carbohydrate or lipid.
Teacher tip The various carbohydrate structures were obtained from the following electronic resources: • • •
commons.wikimedia.org http://www.nature.com/pj/journal/v43/ n12/images/pj201196f3.jpg http://chemwiki.ucdavis.edu/@api/deki/ files/522/260px-Cellulose_strand.jpg? size=bestfit&width=352&height=310&r evision=1
Images for the various lipid structures were obtained from the following electronic resources: • https://upload.wikimedia.org, • http://www.mikeblaber.org/oldwine/ BCH4053/Lecture13/triglyceride.jpg, https://my.bpcc.edu/content/blgy225/ Biomolecules/phospholipid.gif
Biographical Notes FLORENCIA G. CLAVERIA, Ph.D. Team Leader
DAWN T. CRISOLOGO Team Leader
Dr. Florencia G. Claveria is the current Chair of the CHED Technical Panel for Biology and Molecular Biology. She is also member of the Commission’s Technical Panel for Math and Science. She is currently Vice Chancellor for Academics, Research, and Operations at the De La Salle Araneta University. She is a full professor at the De La Salle University-Manila where she served as Dean of the College of Science for 6 academic years. Dr Claveria finished her doctorate in Biological Sciences at the University of Cincinnati, through a Fulbright-Hays grant. She completed her master’s in Zoology at the Ghen State University, through a grant from the Government of Belgium. She earned her bachelor’s degree in Biology at St. Louis University. Her written scholarly works include contributions to academic publications such as the Philippine Textbook of Medical Parasitology, Journal of Protozoology Research, and The Journal of Veterinary Medical Science.
Ms. Dawn Crisologo is a Special Science Teacher at the Philippine Science High School-Main Campus in Diliman, Quezon City and specializes in advanced topics in Ecology, Evolution and Biodiversity, Anatomy, Physiology, and Methods in Science and Technology Research. She is a member of the Asian Association of Biology Educators, Wildlife Conservation Society of the Philippines, and Biology Teachers Association of the Philippines. Her works are included in The Philippine BIOTA Journal and three editions of the Science Blast textbook. Ms. Crisologo is currently finishing her master’s in Environmental Science at the University of the Philippines Diliman. She completed her bachelor’s degree in Biology at the same university.
CHUCKIE FER CALSADO Writer Mr. Chuckie Fer Calsado is Special Science Teacher IV at the Philippine Science High School Main Campus where he has been teaching for 8 years. He is a member of biological organisations like the Biology Teachers Association of the Philippines, the Asian Association for Biology Education, and Concerned Artists of the Philippines among many others. He has published academic papers such as Implication of Students’ Cognitive Style, Personal Demographics, Values and Decision Making in Environmental Education and the Role of Education in the Prevention of Child Trafficking in Nepal. Mr. Calsado finished his Master’s in Bioethics at the Monash University and his bachelor’s degree in Biology at the University of the Philippines DIliman. 184
AILEEN C. DELA CRUZ Writer
JANET S. ESTACION, Ph.D. Writer
Ms. Aileen Dela Cruz has been serving as the Science Research Analyst at the Philippine Science High School - Main Campus since 2004. Her academic interests range from microbiology, food safety and nutrition, and laboratory safety and she has been involved in trainings and conferences on the same fields of study. Her published scholarly works include series of textbooks on 21st Century Learning. Ms. Dela Cruz earned her bachelor’s degree in Biology at the University of the Philippines Baguio.
Dr. Janet Estacion is current Officer-in-Charge at the Institute of Marine and Environmental Science in Silliman Unive
DOREEN D. DOMINGO, PH.D. Writer Dr. Doreen D. Domingo is a Professor at the Mariano Marcos State University where she teaches both in the graduate and undergraduate levels. She is currently the Chief of Alumni Relations for the university. Dr. Domingo finished her doctorate in Biology (magna cum laude) at St. Louis University through a research grant from CHED and the Microbial Forensics and Biodefense Laboratory, Indiana University. She completed her Doctor of Education on Educational Management, her master’s degree in Education major in Biology, and her bachelor’s degree in Biology at the Mariano Marcos State University. Dr. Domingo’s scholarly works were published on the International Referred Journal and the National Referred Journal.
rsity where she has been teaching for 30 years now. She headed researches on marine conservation and the recovery of reefs. Her scholarly works appeared on different publications such as the Philippine Science Letters and the Silliman Journal. Dr. Estacion earned her doctorate degree in Zoology at the James Cook University of North Queensland. She completed her master’s degree in Marine Biology at the University of the Philippines Diliman and her bachelor’s degree in Biology at the Silliman University.
MARY JANE C. FLORES, Ph.D. Writer Dr. Mary Jane C. Flores is Assistant Professor 3 at the College of Science in the De La Salle University where she has been teaching for 20 years now. Her published works include researches on parasitology, climatology, and community nutrition. Dr Flores has conducted and attended seminars on Biology in the country and abroad, including the Training on Biological Control at the US Department of AgricultureAgricultural Research Service and Congress meetings on Parasitology. She is a two-time recipient of the Don Ramon J. Araneta Chair in Ecology among other citations. Dr. Flores earned her Doctorate, Master’s, and Bachelor’s degrees in Biology at the De La Salle University.
JOHN DONNIE RAMOS, Ph.D. Technical Editor
JUSTIN RAY M. GUCE Writer
Mr. Justin Ray Guce is a Special Science Teacher I at the Philippine Science High School Main Campus in DIliman, Quezon City where he teaches for 9 years. He has served as a Trainer of student representatives for Science Olympiad competitions and has delivered presentations in a number of Biology workshops and conventions. Mr Guce is a member of the Wildlife Conservation Society of the Philippines and the Biology Teachers Association of the Philippines. Mr Guce is currently finishing his master’s in Biology Education at the University of the Philippines Diliman where he also graduated his bachelor’s degree in Biology.
NOLASCO H. SABLAN Writer Mr. Nolasco Sablan is Teacher III at the Parada National High School and is a DepEd teacher for 11 years now. He has worked as resource speaker, trainer, and writer for different institutions in the education sector, including the Ateneo de Manila University, Metrobank Foundation Inc., and the Department of Education. Mr. Nolasco Sablan earned his master’s degree in Biology Education at the Ateneo de Manila University and completed his bachelor’s degree in Education major in General Science at the Philippine Normal University.
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Dr. John Donnie Ramos is a Member of CHED’s Technical Panel for Biology and Microbiology and Board Member of the Philippine Society for Biochemistry and Molecular Biology. He is currently the Dean of the College of Science at the University of Santo Tomas where he teaches molecular biology, immunology and genetics, and allergology. Dr. Ramos completed his doctorate in Molecular Biology at the National University of Singapore. He finished his master’s degree in Biological Sciences at the University of Santo Tomas and his bachelor’s degree in Biology at the Philippine Normal University. Dr. Ramos is recipient of the NAST-TWAS Prize for Young Scientist in the Philippines in 2010, and Outstanding Young Scientist by the National Academy of Science and Technology in 2005.
JOY R. JIMENA Copyreader Ms. Joy Jimena is currently Planning Officer II at the Information Management Bureau of the Department of Social Welfare and Development. She also previously worked with other government agencies such as the Department of National Defense and Philippine Commission on Women, and Social Security System. Ms. Jimena graduated at the University of the Philippines Diliman with a degree in Public Administration.
RENAN U. ORTIZ Illustrator Mr. Renan Ortiz is a teacher and visual artist who has collaborated in local and international art exhibitions such as the SENSORIUM at the Ayala Museum, Populus in Singapore, Censorship_2013 Move On Asia in South Korea, and the Triumph of Philippine Art in New Jersey, USA. Mr. Ortiz’s solo exhibitions include versereverse at the Republikha Art Gallery. He first completed his bachelor’s degree in Political Science at the University of the Philippines Manila before finishing his bachelor’s degree in Fine Arts major in Painting at the University of the Philippines Diliman. Mr. Ortiz is an awardee of the Cultural Center of the Philippines’ CCP Thirteen Artists Awards in 2012.
DANIELA LOUISE B. GO Illustrator Ms Daniela Louise Go is a freelance illustrator and graphic designer, specializing on graphic design, brand and campaign design, and copywriting. She has worked as illustrator for Stache Magazine, Philippine Daily Inquirer, and Summit Media Digital. Ms Go is a member of organisations such as the UP Graphic and UP Grail in which she also served as designer and illustrator. Her works have been part of art exhibitions including Freshly Brewed, Wanton Hypermaterialism, and Syntheses 2014: Graduate Exhibit. Ms. Go graduated her bachelor’s degree in Fine Arts Major in Visual Communication at the University of the Philippine Diliman.
