Question

the enzyme pepsin catalyzes the breakdown of protein but does not affect the breakdown of lipids. what affects why enzymes catalyze reactions involving some types of molecules but not others?
○ the temperature of the environment
○ the shapes of the molecules involved
○ the amount of atp available for the reaction
○ the number of molecules present in the reactants

Explanation:

Enzymes are specific in their action due to the lock - and - key or induced - fit model. The active site of an enzyme has a specific shape that is complementary to the shape of the substrate (the molecule it acts on). Pepsin acts on proteins but not lipids because the shape of protein molecules (substrate) fits the active site of pepsin, while lipid molecules do not. Temperature affects the rate of enzyme - catalyzed reactions (like denaturing the enzyme at extreme temps) but not the specificity of which molecules the enzyme acts on. ATP is related to energy transfer in cells and not enzyme specificity. The number of reactant molecules affects the rate of reaction (based on collision theory) but not the enzyme's specificity for certain molecule types.

Answer:

B. the shapes of the molecules involved