chapter 5 questions Flashcards
review the 6 different types of functions that proteins in plasma membrane can perform.
attachment to the cytoskeleton and ECM, signal transduction, enzymatic activity, cell-cell recognition, intercellular joining and transport
why is diffusion across a membrane called passive transport?
the cell dos not expend energy to transport substances that are diffusing down their concentration gradients
indicate the direction of net water movement between two solutions - a 0.5% sucrose solution and a 2% sucrose solution - separated by a membrane not permeable to sucrose
from the 0.5% sucrose solution (lower solute concentration) to the 2% sucrose solution (higher solute concentration)
explain the function of the contractile vacuoles in the fresh-water paramecium in terms of what you have just learned about water balance in cells
because they are specific for the solutes they transport, the number kinds of transport proteins affect a membranes permeability to various solutes
why are aquaporins important in kidney cells?
kidney cells must reabsorb a large amount of water when producing urine
cells actively transport Ca2+ out of the cell. is calcium more concentrated inside or outside of the cell?
outside: active transport moves calcium against its concentration gradient
as cells grow, its plasma membrane expands. does this involve endocytosis or exocytosis?
exocytosis: when a transport vesicle fuses with the plasma membrane, its contents are released and the vesicle membrane adds to the plasma membrane
how does the second law of thermodynamics explain the difference of a solute across a membrane?
diffusion across a membrane results in equal concentration of solute, which is a more disordered arrangement (higher entropy) than a high concentration on one side and a low concentration on the other.
cellular respiration is an exergonic process. remembering that energy must be conserved, what becomes of the energy extracted from food during cellular respiration?
some of it is stored in ATP molecules; the rest is released as heat
explain how ATP transfers energy from exergonic to endergonic processes in the cell.
exergonic processes phosphorlate ADP to form ATP. ATP transfers energy to endergonic processes by phosphorylating other molecules.
explain how an enzyme speeds up a specific reaction.
an enzyme lowers the activation energy needed for a reaction when its specific substrate enters its active site. with an induced fit, the enzyme strains bonds that need to break or positions substrates in an orientation that aids the conversion of reactants to products.
explain an advantage of feedback inhibition to a cell.
it prevents the cell from wasting valuable resources by synthesizing more of a particular product that is needed.
what determines whether enzyme inhibition is reversible or irreversible?
if the inhibitor binds to the enzyme with covalent bonds, the inhibition is usually irreversible. when weak chemical interactions bind inhibitor and enzyme, the inhibition is reversible
