Question 1

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

Accepted Answer

They lower the activation energy ($$\Delta G$$^{\ddagger}$$) required to reach the transition state.

Question 2

A patient’s blood enzyme is denatured after a high fever. Which property of enzymes explains this loss of function?

Accepted Answer

Enzymes are globular proteins whose structure is sensitive to temperature changes.

Question 3

Which of the following statements about enzyme-substrate interactions is correct?

Accepted Answer

The lock and key model suggests the enzyme’s active site is rigid and does not change shape.

Question 4

Which of the following is NOT a characteristic that distinguishes enzymes from chemical catalysts?

Accepted Answer

Enzymes always require extreme pH to function.

Question 5

Consider the reaction coordinate diagram for a catalyzed and uncatalyzed reaction. What does the difference in the height of the peaks represent?

Accepted Answer

The reduction in activation energy ($$\Delta G$$^{\ddagger}$$) due to the enzyme.

Question 6

Which of the following best describes a holoenzyme?

Accepted Answer

An enzyme with its cofactor, forming the active complex.

Question 7

A competitive inhibitor affects enzyme activity by:

Accepted Answer

Competing with the substrate for the active site.

Question 8

Which of the following is an example of an enzyme classified as a lyase (EC 4)?

Accepted Answer

Aconitase hydratase (EC 4.2.1.3)

Question 9

Which of the following interactions is NOT typically involved in enzyme-substrate binding?

Accepted Answer

Covalent bonds

Question 10

A mutation causes an enzyme’s active site to lose its geometric complementarity. What is the most likely result?

Accepted Answer

The enzyme will lose its substrate specificity and catalytic activity.

Question 11

Which of the following best describes feedback inhibition in metabolic pathways?

Accepted Answer

The end product of a pathway inhibits an enzyme that acts early in the pathway.

Question 12

Which of the following statements about enzyme nomenclature is correct?

Accepted Answer

The systematic name includes the substrate(s) and the type of reaction catalyzed.

Question 13

Which of the following is a cofactor that is a metal ion?

Accepted Answer

Mg$$^{2+}$$

Question 14

Which of the following best explains why enzymes are more sensitive to changes in pH and temperature than fibrous proteins?

Accepted Answer

Enzymes have complex tertiary and quaternary structures that are essential for their function.

Question 15

Which of the following is true regarding the effect of an enzyme on the equilibrium of a reaction?

Accepted Answer

Enzymes do not change the equilibrium constant ($$K_{eq}) of a $$reaction.

Question 16

A scientist observes that an enzyme-catalyzed reaction proceeds at a much higher rate at pH 7 than at pH 4. What is the most likely explanation?

Accepted Answer

The enzyme’s active site is denatured at pH 4.

Question 17

Which of the following is a correct statement about the induced fit model of enzyme action?

Accepted Answer

The enzyme’s active site changes shape to better fit the substrate upon binding.

Question 18

Which of the following is NOT a function of globular proteins?

Accepted Answer

Structural support in connective tissue

Question 19

Which of the following best describes the role of cofactors in enzyme function?

Accepted Answer

Cofactors are non-protein molecules or ions required for enzyme activity.

Enzymes and Catalysis: Structure, Function, and Regulation

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