Question 1

Which of the following best describes how enzymes increase the rate of a chemical reaction?

Accepted Answer

They lower the activation energy ($$E_a) by $$stabilizing the transition state.

Question 2

A patient is prescribed a drug that acts as a competitive inhibitor for an essential enzyme. Which of the following strategies could most effectively overcome the inhibition?

Accepted Answer

Increase the concentration of the substrate.

Question 3

Which class of enzyme catalyzes the following reaction?

$$\mathrm{CH_3CH_2OH + NAD^+ \longrightarrow CH_3CHO + NADH + H^+}$$

Accepted Answer

Oxidoreductase

Question 4

Which of the following statements about enzyme specificity is correct?

Accepted Answer

Enzymes are highly specific, usually catalyzing only one type of reaction for a particular substrate.

Question 5

Which of the following is an example of feedback inhibition in metabolic pathways?

Accepted Answer

A product of a pathway binds to an allosteric site of an early enzyme, decreasing its activity.

Question 6

Which of the following best distinguishes between the lock-and-key and induced fit models of enzyme action?

Accepted Answer

The lock-and-key model suggests the active site is rigid, while the induced fit model suggests both enzyme and substrate can change shape for optimal binding.

Question 7

A patient with a deficiency in vitamin B$$_3 ($$niacin) would have trouble producing which important metabolic cofactor?

Accepted Answer

NAD$$^+$$

Question 8

Which of the following statements about zymogens (proenzymes) is correct?

Accepted Answer

They are inactive precursors that require covalent modification to become active.

Question 9

Which of the following is a correct match between enzyme class and reaction type?

Accepted Answer

Isomerase: rearranges atoms within a molecule

Question 10

Which of the following best explains why enzymes are not consumed in the reactions they catalyze?

Accepted Answer

Enzymes are regenerated after each reaction cycle and can catalyze multiple rounds of reaction.

Question 11

A scientist is studying an enzyme that requires zinc ions for activity. What is the role of zinc in this context?

Accepted Answer

Zinc acts as a cofactor.

Question 12

Which of the following statements about water-soluble and fat-soluble vitamins is correct?

Accepted Answer

Fat-soluble vitamins can accumulate in body tissues and may cause toxicity if consumed in excess.

Question 13

Which of the following is a real-world example of an irreversible enzyme inhibitor?

Accepted Answer

Penicillin binding covalently to transpeptidase in bacteria.

Question 14

Which of the following best describes the effect of increasing substrate concentration on an enzyme-catalyzed reaction when all enzyme active sites are occupied?

Accepted Answer

The reaction rate will reach a maximum and no longer increase.

Question 15

Which vitamin is required for the synthesis of zymogens involved in blood clotting?

Accepted Answer

Vitamin K

Question 16

A patient is found to have prolonged bleeding time and easy bruising. Which vitamin deficiency is most likely responsible?

Accepted Answer

Vitamin K

Question 17

Which of the following statements about enzyme regulation is correct?

Accepted Answer

Feedback inhibition involves the end product of a pathway inhibiting an earlier enzyme in the pathway.

Question 18

Which of the following is a correct match between a vitamin and its biological function?

Accepted Answer

Vitamin D: Regulates calcium and phosphorus absorption

Question 19

Which of the following best describes the role of kinases in enzyme regulation?

Accepted Answer

Kinases add phosphate groups to enzymes, often altering their activity.

Question 20

A mutation causes an enzyme to lose its ability to bind its substrate, but the enzyme's overall structure is unchanged. Which part of the enzyme is most likely affected?

Accepted Answer

The active site

Chapter 20: Enzymes and Vitamins – Structure, Function, and Regulation

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