Question 1

Which of the following best describes how a catalyst affects a chemical reaction?

Accepted Answer

It increases the rate of the reaction by lowering the activation energy without being consumed in the process.

Question 2

Which enzyme class is responsible for transferring a phosphate group from ATP to glucose in the first step of glycolysis?

Accepted Answer

Transferases

Question 3

The induced fit model of enzyme-substrate interaction differs from the lock-and-key model in that:

Accepted Answer

The enzyme changes conformation upon substrate binding to better fit the substrate.

Question 4

Which of the following is NOT a mechanism by which enzymes achieve rate acceleration?

Accepted Answer

Increasing the temperature of the reaction environment.

Question 5

Which statement best describes uncompetitive inhibition?

Accepted Answer

The inhibitor binds only to the enzyme-substrate complex, reducing both $$K_m$$ and $$V_{max}.$$

Question 6

Which of the following is an example of irreversible enzyme inhibition?

Accepted Answer

Diisopropyl fluorophosphate (DFP) binding to acetylcholinesterase.

Question 7

Which regulatory mechanism involves the end product of a metabolic pathway inhibiting an enzyme that acts early in the pathway?

Accepted Answer

Feedback inhibition

Question 8

Phosphorylation and dephosphorylation of enzymes are examples of:

Accepted Answer

Reversible covalent modification

Question 9

Which of the following statements about allosteric enzymes is TRUE?

Accepted Answer

They are usually multisubunit proteins that change conformation upon effector binding.

Question 10

Which of the following best describes a ribozyme?

Accepted Answer

An RNA molecule with catalytic activity.

Question 11

Which of the following is a plausible consequence of a mutation that prevents phosphorylation of a key regulatory enzyme?

Accepted Answer

The enzyme may be locked in either an active or inactive state, disrupting normal regulation.

Question 12

Which of the following statements about enzyme cofactors is CORRECT?

Accepted Answer

Cofactors can be metal ions or small organic molecules required for enzyme activity.

Question 13

Which of the following is an example of an irreversible covalent modification that activates an enzyme?

Accepted Answer

Proteolytic cleavage of a zymogen

Question 14

Which of the following best explains why substrate-level control is considered a crude means of enzyme regulation?

Accepted Answer

A large change in substrate concentration is required to significantly alter enzyme activity.

Question 15

Which of the following mechanisms is NOT typically involved in enzymatic catalysis?

Accepted Answer

Increasing the entropy of the substrate.

Question 16

Which vitamin-derived coenzyme is involved in oxidation-reduction reactions and is associated with riboflavin?

Accepted Answer

Flavin mononucleotide (FMN)

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