AQA A level Biology Revision Questions and Answers.

AQA A level Biology Revision Questions and Answers.: Prevent entry of/binding of substrate to active site; Therefore fewer/no enzyme-substrate complexes formed; Describe and explain how an increase in temperature affects the rate of an enzyme controlled reaction. [5] -ANSWER Rate of reaction increases; Increasing temperature increases rate of movement of molecules/ kinetic energy; Collide more often/substrate enters active site more often/more enzyme-substrate complexes formed; Up to optimum; Rate of reaction decreases; High temperatures cause denaturation/loss of tertiary structure/3D structure; By breaking specified bonds (not peptide bond); Active site altered/substrate cannot bind/fit/ An enzyme catalyses only one reaction. Explain why [2] -ANSWER (Enzyme has) active site; Only substrate fits (the active site); Describe the induced fit model of enzyme action. [2] -ANSWER Active site / enzyme not complementary; Active site changes (shape) / is flexible; (Change in enzyme allows) substrate to fit / E-S complex to form; Describe one way that the lock and key model is different from the induced fit model. [1] -ANSWER Active site does not change (shape) / is fixed (shape) / is rigid / does not wrap around substrate / (already) fits the substrate / is complementary (before binding); Explain why the rate of reaction of an enzyme is low away from its optimum pH. [3] -ANSWER (change in pH) leads to breaking of bonds holding tertiary structure/ changes charge on amino acids; enzyme/protein/active site loses shape/denatured; substrate will not bind with/fit active site; fewer/no ES complexes formed; A protein molecule contains 150 amino acids. What is the total number of peptide bonds in this molecule? [1] -ANSWER 149