Cell Membrane *go back to cell membrane notes -cell membrane also has carbohydrates; mainly attached to marker proteins Transport: 1. Diffusion: movement of molecules from high to low concentration until equilibrium is reached 2. Osmosis: movement of water across a membrane. Osmotic pressure: pressure due to water. Passive transport: transport that does not require energy and is with the concentration gradient (high to low) 3. Facilitated Diffusion: diffusion with the help of carrier/channel proteins. No energy required (also called Selective transport) Channel proteins: (2 types; can open or close) voltage-gatedchange in electric impulse will cause them to open; ex. Nerve cells, and chemical-gatedopen and close in response to chemicals (such as food, glucose). 4. Active transport: transport that requires energy and is against the concentration gradient (low to high) Ex. of Passive transport: diffusion, osmosis, facilitated diffusion Ex. of Facilitated diffusion: transport of sugars Ex. of Active transport: 1. Sodium-potassium pump (pumps Na+ and K+ ions) 2. Proton pump (pump H+) 3. Exocytosis (large molecules transported out) 4. Endocytosis (large molecules transported in) 3 types of Endocytosis: Pinocytosis (cell drinking; liquid) Phagocytosis (bacteria engulfed by white blood cells lysosomes then destroy the bacteria Receptor-mediated Endocytosis (receptor required) Passive Active 1. Does not require energy 1. Requires energy 2. With concentration gradient (high to 2. Against concentration gradient (low to low) high) 3. Can be 2 way (both directions, into/out 3. Only 1 way (either in or out) of cell) 4. Ex. transport of sugars by facilitated 4. Ex. proton pump (protons) diffusion Sodium-Potassium pump (Na+, K+)

Hypotonic: low solute concentration Hypertonic: high solute concentration Isotonic: equal

Water always moves from high water concentration to low water concentration until equilibrium is reached. Water always moves from low solute concentration to high solute concentration until equilibrium is reached. Solute always moves from high solute concentration to low solute concentration until equilibrium is reached. *The process of regulating water going in and out of a cell (how they maintain balance) is osmoregulation. *The solute moves but does not change volume. *Water changes volume.

high |- - - - - - - - - - - - - - - | low solute | 1.0 M | 0.5 M | solute concentration | NaCl NaCl | concentration | | | |__________________| ------------- Solute (NaCl) (until equilibrium is reached; 0.75 M) ------------Water |- - - - - - -| | 0.5 | | 1.0 | |________| Hypertonic Solution Hypotonic cell (water moves out of cell; cell shrinks)

|- - - - - - -| | 1.0 | | 1.0 | |________| Isotonic Solution

|- - - - - - -| | 2.0 | | 1.0 | |________| Hypotonic Solution Hypertonic cell (swells, bursts)

*Cell placed in hypertonic solution will shrink *Isotonic cell stays the same *Cell placed in hypotonic solution will swell, burst Water moves through gaps in the phospholipid bilayer Sugars go in by facilitated diffusion (Selective transport, example of passive transport) Gases diffuse in (simple diffusion) Ions transported by Active Transport Cell membrane is semipermeable (control to certain extent) Plant cell in isotonic solution is flaccid

Plant cell in hypotonic solution becomes turgid (does not burst because of cell wall)no lysing (bursting) When equilibrium is reached there is no net change in solute and water concentration Pumps: A sodium-potassium pump will only pump sodium out and potassium in (for every 3 sodiums out, 2 potassiums in). o To bring sodium back in Na ions group with sugar (glucose); brought back in by facilitated diffusion (by using couple-channels) Proton pump: helps to produce ATP (energy for cells) in cells by process called chemiosmosis. Receptor-mediated Endocytosis: ex. excess cholesterol transported and stored in liver cell by Receptor-mediated endocytosis (will have high cholesterol if receptor-mediated endocytosis is messed up) o Hypercholesterolemia: high blood cholesterol ATP Adenosine Adenine (base)

Ribose (sugar)

3 Phosphate groups

3

2

1

High energy bond (when bond is broken, energy released) Adenosine Tri Phosphate (temporary source of energy; like ATM machine) Long term energy: carbohydrates and fat ADP

energy Adenosine diphosphate (ADP) + phosphate --------- Adenosine triphosphate (ATP) (Partially charged battery------------ Fully charged battery) ATP ADP + P + Energy (7.3 Kcalory) Working muscle regenerates and uses (recycles) 10 million ATP molecules/second/cell If cells need energy they breakdown ATP When cells want to store energy they form/make ATP (using ADP+P)

Energy (capacity to do work) Metabolism: made up of anabolic pathways (consume energy/absorb to build macromolecules; ex. photosynthesis) and catabolic pathways (release energy by breaking down complex macromolecules; ex. cellular respiration) o Plants carry out both, animals mostly catabolic Reactions are either: Endergonic (absorb energy) or Exergonic (release energy) reactions; | activation | | B energy (needed | A AB energy | energy to start | |A reaction) | B |_______________ |_______________ Energy consumed; input Ex. cellular respiration (mainly found in) Ex. mainly seen in photosynthesis (hump b/c extra energy needed) potential energy (position) kenetic energy (movement) First Law of Thermodynamics: energy can neither be created or destroyed, but can be changed from one form to another Second Law of Thermodynamics: Entropy (disorder) in the universe is always increasing Free Energy: Amount of total energy that is available to do work o While doing work (energy transformations), energy is lost in the form of heat | activation (start up) | energy push | reactants over | energy barrier) |_______________ Uncatalyzed reaction (no enzyme) So, big activation energy So, long reaction

| | | | |_______________ Catalyzed reaction (enzyme) Reaction faster b/c activation energy shorter/smaller

Enzymes: Biocatalysts that speed up a reaction by lowering the activation energy Enzyme

A (reactant) B (product) A (substrate) --------- B (product) Substrate: reactant on which an enzyme acts on Enzymes specific; recognize a specific substrate Active site (where substrate binds); also called catalytic center Enzymes function because of their structure (tertiary structure); gives each protein unique shape Enzyme substrate *Enzymes and substrate fit into each other like a “lock and key” (lock and key model) *Substrate may also induce an enzyme’s shape to make it fit (induced fit model) Enzymes are recycled; carry out reaction for only a certain amount of time o If you change enzyme shape, it’s denatured (with lock and key model); is reversible in some cases (can be renatured) Some enzymes can carry out reversible reaction AB Enzyme | maximum (rate of reaction) Max reached b/c of enzyme rate of | saturation rxn. | *Most enzymes work | on organic molecules/ |____________________ compounds (organicC-C bond) Time Every enzyme has its optimum pH and temperature o Most enzymes denature at higher temps. o Most enzymes function best at neutral pH (except some, like stomach enzymes, that work at low pH) | | | | |_______________ 10 20 30 40 50 Temp

| | | | |_______________ 1

2

3 4 pH

5

*enzyme works best at pH 3 and temp. 25 degrees C *pH 1 and 5 lowest (b/c denatured) and lowest temp. is 10 and 40 Some enzymes need nonprotein (inorganic) helpers, such as Fe, Zn, Cu, etc., called cofactors Some enzymes need organic helpers called coenzymes; ex. some vitamins Inhibitors: anything that will stop enzyme from functioning (prevent enzyme activity) 2 types:

1. competitive: bind to active site; substrate can not bind (block active site preventing enzyme activity) 2. Noncompetitive: bind to enzyme anywhere on enzyme other than active site, changing active site’s shape; enzyme can’t carry out activity Enzyme activity depends on: pH, temp., salt concentration, amount of substrate, amount of enzyme, presence of inhibitors, presence of cofactors/coenzymes, and presence of activators Allosteric Enzymes: o Most have quaternary structure (2 or more polypeptides) o 2 sites: active site and allosteric/regulatory site o Can be regulated by product o Shut down when there’s excess products Enzyme keeps going until many P S  P E P P P Active site o Feed Back Inhibition: product fed back to enzyme (in cellular respiration rxn; make ATP (product that comes back, shut down enzyme)  Active site changed; can’t Back on (once product gone) recognize substrate (shut down ezyme) AB BC CD DE

Chain of reactions are called biochemical pathway (product of one reaction becomes reactant of next reaction)

Cooperativity: single enzyme with multiple active sites or multiple catalytic sites Multienzyme Complex: team of enzymes working together  seen mainly in biochemical pathway