Question 1

Refer to the first image. Which statement best describes what is happening to the substrate and product concentrations over time in an enzyme-catalyzed reaction?

Accepted Answer

The substrate concentration decreases while the product concentration increases until equilibrium is reached, after which both remain constant.

Question 2

Based on the second image, which graph (a, b, or c) corresponds to a reaction with an equilibrium constant $$K_{eq} \u003c 1$$?

Accepted Answer

Graph b

Question 3

Which of the following best describes the role of an enzyme as depicted in the enzyme-substrate complex diagram (lock-and-key model)?

Accepted Answer

The enzyme binds the substrate, forms a temporary complex, and releases the product without being consumed.

Question 4

In the reaction coordinate diagram comparing catalyzed and uncatalyzed reactions, what is the main effect of the enzyme?

Accepted Answer

It lowers the activation energy ($$E_A) $$required to reach the transition state.

Question 5

Which of the following is NOT a way that enzymes lower the activation energy ($$E_A) of a $$reaction?

Accepted Answer

Increasing the randomness (entropy) of substrates.

Question 6

Which of the following statements about enzyme-substrate binding energy ($$\Delta G_B) is $$TRUE?

Accepted Answer

It is the energy released by noncovalent interactions between enzyme and substrate, which helps lower the activation energy.

Question 7

Which of the following is a potential disadvantage for an enzyme having too high an affinity for its substrate (as in the lock-and-key model)?

Accepted Answer

The ES complex could be too stable, resulting in a large activation energy to reach the transition state.

Question 8

Refer to the pH activity profile for pepsin and chymotrypsin. Which of the following best explains why these enzymes have different optimal pH values?

Accepted Answer

Their active site amino acids have different ionization properties, which are affected by pH.

Question 9

Which of the following best describes catalysis by proximity?

Accepted Answer

Catalysis through increasing the concentration of substrates in the enzyme active site.

Question 10

Which class of enzyme catalyzes the transfer of a phosphate group from ATP to a substrate?

Accepted Answer

Transferase

Question 11

Which of the following statements about enzyme kinetics is FALSE?

Accepted Answer

Enzymes push the reaction equilibrium toward product formation.

Question 12

Which of the following best describes the energy of activation ($$E_A) $$for a reaction?

Accepted Answer

The difference in free energy between the substrate and the transition state.

Question 13

Which of the following is NOT one of the six major classes of enzymes?

Accepted Answer

Polymerases

Question 14

Which of the following statements about enzyme inhibitors is TRUE?

Accepted Answer

All the above are true.

Question 15

Which of the following best describes the effect of a noncompetitive inhibitor on enzyme kinetics?

Accepted Answer

It decreases Vmax but does not change Km.

Question 16

Which of the following statements about allosteric enzymes is FALSE?

Accepted Answer

Allosteric enzymes are regulated primarily by covalent modifications.

Question 17

Which of the following best describes the effect of phosphorylation on the activity of glycogen phosphorylase?

Accepted Answer

Phosphorylation activates the enzyme by favoring the R state.

Question 18

Which of the following is TRUE regarding the regulation of muscle glycogen phosphorylase?

Accepted Answer

AMP acts as a positive allosteric effector, activating the enzyme during muscle contraction.

Enzyme Function and Kinetics: Principles and Mechanisms

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