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AP Biology Test, Chapter 7

front 1 Which macromolecules make up membranes?	back 1 lipids and proteins carbohydrates also important
front 2 most abundant lipid in most membranes	back 2 phospholipids
front 3 amphipathic	back 3 has both a hydrophilic ("water loving") and hydrophobic ("water fearing) region
front 4 how can a phospholipid bilayer exist as a stable boundary between two aqueous compartments?	back 4 the molecular arrangement shelters the hydrophobic tails of the phospholipids from water while exposing the hydrophilic heads to water

front 5 fluid mosaic model	back 5 describes membrane as fluid, with proteins embedded in or associated with the phospholipid bilayer
front 6 plasma membrane	back 6 selectively permeable it allows some substances to cross more easily than it does others
front 7 membranes are predominantly made of...	back 7 phospholipids and proteins held together by weak interactions cause the membrane to be fluid
front 8 phospholipids	back 8 provide a hydrophobic barrier that separates the cell from its liquid environment hydrophilic molecules cannot easily enter the cell, but hydrophobic molecules can

front 9 cholesterol	back 9 hydrophobic steroid found embedded in animal membranes helps membranes resist changes in fluidity when the temperature changes at high temp - makes membrane less fluid at low temp - helps membrane retain fluidity
front 10 proteins	back 10 embedded in the membrane can serve as transport channels to move materials across hydrophobic interior of the phospholipid bilayer can act as molecular receptors to bind to signaling molecules (ligands)
front 11 peripheral proteins	back 11 loosely bound to membrane's surface not embedded in the lipid bilayer
front 12 membrane carbohydrates	back 12 crucial in cell-cell recognition important in the sorting of cells into tissues in an animal embryo basis for rejection of foreign cells by the immune system short, branched chains fewer than 15 sugar units

front 13 intergral proteins	back 13 penetrate the hydrophobic interior of the lipid bilayer
front 14 glycolipids	back 14 membrane carbohydrate chains covalently bonded to lipids short, branched
front 15 glycoproteins	back 15 membrane carbohydrate chains covalently bonded to proteins
front 16 integrins	back 16 cell-surface receptor proteins

front 17 non-polar molecules (hydrophobic)...	back 17 can dissolve in the hydrophobic interior of the phospholipid bilayer cross the membrane easily examples: hydrocarbons, oxygen, carbon dioxide
front 18 hydrophobic core of the membrane...	back 18 impedes the passage of ions and polar molecules (hydrophilic)
front 19 transport proteins	back 19 enable hydrophilic substances to avoid the lipid bilayer and pass through span the membrane are specific, like enzymes, for the substances they transport
front 20 aquaporins	back 20 transport (channel) proteins accelerate the speed at which water can cross membranes (three billion water molecules per second)

front 21 passive diffusion	back 21 substance travels from where it is more concentrated to where it is less concentrated diffuses down its concentration gradient does not require energy relies only on the thermal motion energy intrinsic to the molecule in question
front 22 concentration gradient	back 22 process in which particles move from an area of high concentration to low concentration region along which the density of a chemical substance increases or decreases
front 23 osmosis	back 23 the diffusion of water across a selectively permeable membrane water diffuses from the solution with the less concentrated solute to that of the more concentrated solute
front 24 isotonic solution	back 24 no net movement of water across the plasma membrane water crosses the membrane at the same rate in both directions

front 25 hypertonic solution	back 25 cell loses water to surroundings (shrivels, may die) more solutes in the water around the cell
front 26 hypotonic solution	back 26 water will enter the cell faster than it leaves (will swell and may burst) fewer solutes around the cell
front 27 water moves from...	back 27 Hypo-> Hyper
front 28 ions and polar molecules...	back 28 cannot move easily across the membrane

front 29 facilitated diffusion	back 29 process by which ions and polar molecules diffuse across the membrane with the help of transport proteins
front 30 how do transport proteins work?	back 30 provide a hydrophilic channel through which the molecules in question can pass bind loosely to molecules in question and carry them through the membrane
front 31 active transport	back 31 substances are moved against their concentration gradient low concentration -> high concentration requires energy, usually in the form of ATP
front 32 sodium-potassium pump	back 32 good example of active transport transmembrane protein pumps sodium out of the cell and potassium ions into the cell necessary for proper nerve transmission and is a major energy consumer in the body

front 33 membrane potential	back 33 difference in electrical charge across a membrane expressed in voltage inside of the cell is negatively charged compared with outside the cell
front 34 why are positively charged ions on the outside of the cell attracted to the inside of the cell?	back 34 inside of cell is negatively charged
front 35 what two forces drive the diffusion of ions across a membrane?	back 35 chemical force - ion's concentration gradient voltage gradient across the membrane - attracts positively charged ions and repels negatively charged ions
front 36 chemical force	back 36 ion's concentration gradient

front 37 voltage gradient	back 37 across the membrane attracts positively charged ions and repels negatively charged ions
front 38 combination of forces acting on ion forms...	back 38 electrochemical gradient
front 39 cotransport	back 39 ATP pump that transports a specific solute indirectly drives the transport of other substances substance that was initially pumped across the membrane can do work as it moves back across the membrane by diffusion brings with it a second compound against gradient
front 40 carrier protein	back 40 change shape in a way that shuttles their "passengers" across the membrane

front 41 channel proteins	back 41 function by having a hydrophilic channel that certain molecules or ions use as a tunnel through the membrane
front 42 large molecules are moved across the cell membrane through...	back 42 exocytosis and endocytosis both processes require energy
front 43 exocytosis	back 43 vesicles from the cell's interior fuse with the cell membrane expelling contents
front 44 endocytosis	back 44 cell forms new vesicles from the plasma membrane allows the cell to take in macromolecules examples: engulfing of foreign particles by white blood cells or amoebas reverse of exocytosis

front 45 examples of molecules that pass through phospholipid bilayer using simple diffusion	back 45 CO2 O2
front 46 examples of molecules that pass through phospholipid bilayer using carrier proteins	back 46 glucose
front 47 examples of molecules that pass through phospholipid bilayer using channel proteins	back 47 H+ ions (protein pump)
front 48 bulk transport	back 48 moves large molecules exocytosis and endocytosis requires energy

front 49 what is meant by membrane fluidity?	back 49 membranes are not static sheets of molecules locked rigidly in place they move and shift sideways, hence the "fluid" classification
front 50 how can decrease in temperature affect membrane fluidity?	back 50 membrane becomes more solid phospholipids settle into closely packed arrangement
front 51 how do phospholipids with unsaturated hydrocarbon chains affect membrane fluidity?	back 51 with temperature decrease, membrane still remains fluid kinks in tails don't allow the phospholipids to pack tightly together
front 52 how does cholesterol affect membrane fluidity?	back 52 acts as a "fluidity buffer" resists changes in membrane fluidity that can be caused by changes in temperature at low temperatures - hinders solidification by disrupting the regular packing of phospholipids at moderate temperatures - reduces phospholipid movement, reducing membrane fluidity

front 53 how do phospholipids with saturated hydrocarbon chains affect membrane fluidity?	back 53 saturated carbon tails pack together, increasing membrane viscosity
front 54 major functions of membrane proteins	back 54 transport enzymatic activity signal transduction cell-cell recognition intercellular joining attachment to cytoskeleton and ECM
front 55 transport	back 55 proteins guide and pump substances across the membrane using energy
front 56 enzymatic activity	back 56 enzymes in membrane organized into teams to carry out sequential steps of metabolic pathway

front 57 signal transduction	back 57 signaling molecule binds to receptor may cause receptor to change shape allows message to be relayed
front 58 cell-cell recognition	back 58 glycoproteins act as identification tags recognized by membrane proteins of other cells
front 59 intercellular joining	back 59 membrane proteins hook together to those of the adjacent cell
front 60 attachment to cytoskeleton and ECM	back 60 cytoskeleton elements bind to membrane proteins maintains cell shape stabilizes protein location proteins bind to ECM coordinate cellular changes outside or inside cell

front 61 integrins	back 61 cell surface receptor proteins
front 62 cytoskeleton microfilaments	back 62 thin, solid rods form structural networks when certain proteins bind along the side of other filaments
front 63 ECM fibers	back 63 made up of glycoproteins embedded in a network woven out of proteoglycans
front 64 example of transport proteins being specific	back 64 doesn't allow fructose to pass, a structural isomer of glucose

front 65 diffusion	back 65 the movement of particles of any substance so that they spread out into the available space
front 66 turgid	back 66 healthy state for most plant cells very firm
front 67 flaccid	back 67 no net tendency for water to enter plant wilts limp
front 68 plasmolysis	back 68 plasma membrane pulls away from the cell wall at multiple places as plant cell shrivels causes plant to wilt and can lead to plant death

front 69 why does the plant cell not burst like the red blood cell when placed in a hypotonic solution?	back 69 the plant cell has a cell wall uptake of water is eventually balanced by the wall pushing back on the cell
front 70 summary: sodium-potassium pump	back 70 cytoplasmic Na+ binds to sodium-potassium pump binding of 3 Na+ stimulates phosphorylation by ATP phosphorylation leads to change in protein shape - Na+ is released new shape attracts K+ - K+ binds to extracellular side, triggers release of the phosphate group phosphate group restores protein's OG shape 2 K+ released, cycle repeats with affinity for Na+ once again
front 71 receptor-mediated endocytosis	back 71 enables the cell to acquire bulk quantities of specific substances specialized type of pinocytosis key feature: receptor sites that bind with specific solutes
front 72 phagocytosis	back 72 a cell engulfs a particle by extending a pseudopodia fluid around it, and packaging it within food vesicle

front 73

pinocytosis

back 73

cell continually gulps droplets of extracellular fluid into tiny vesicles formed by infolding of plasma membrane