Question 1

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

Accepted Answer

They provide a surface that lowers the activation energy ($$E_A) $$required for the reaction.

Question 2

A patient is exposed to a nerve gas that irreversibly binds to acetylcholinesterase. What is the most likely cellular consequence?

Accepted Answer

The enzyme will be permanently inactivated, leading to toxic accumulation of acetylcholine.

Question 3

Which of the following statements about the Michaelis–Menten equation is correct?

Accepted Answer

The equation is $$v_0$$ = \frac{V_{max}[S]}{K_m + [S]}$$ and describes the initial velocity as a function of substrate concentration.

Question 4

Which class of enzyme catalyzes the reaction: $$A - PO_4$ + B \rightarrow A + B - PO_4$?

Accepted Answer

Transferases

Question 5

A competitive inhibitor affects enzyme kinetics by:

Accepted Answer

Increasing $$K_m$$ and leaving $$V_{max}$$ unchanged

Question 6

Which of the following best explains why increasing temperature is not a useful strategy for increasing reaction rates in living cells?

Accepted Answer

Cells are isothermal and cannot tolerate large temperature changes without risking protein denaturation.

Question 7

Which of the following is a property shared by all catalysts, including enzymes?

Accepted Answer

They lower the activation energy ($$E_A) $$required for the reaction.

Question 8

A mutation in the active site of an enzyme changes the shape of the pocket. What is the most likely effect?

Accepted Answer

The enzyme will lose substrate specificity and may catalyze unwanted reactions.

Question 9

Which of the following best describes allosteric regulation of an enzyme?

Accepted Answer

A molecule binds to a regulatory site, changing the enzyme's conformation and activity.

Question 10

Which of the following is true about feedback inhibition in metabolic pathways?

Accepted Answer

The final product inhibits an enzyme that acts early in the pathway.

Question 11

Which of the following statements about $$K_m is $$correct?

Accepted Answer

$$K_m is $$the substrate concentration at which the reaction velocity is half-maximal.

Question 12

Which of the following is an example of a coenzyme?

Accepted Answer

A small organic molecule derived from a vitamin

Question 13

Which of the following best explains why the reaction velocity ($$v) $$plateaus at high substrate concentrations?

Accepted Answer

The enzyme is saturated and all active sites are occupied.

Question 14

Which of the following is NOT a property of enzymes?

Accepted Answer

They are consumed in the reaction.

Question 15

A patient has a genetic defect that prevents the synthesis of a required coenzyme. Which of the following is a likely consequence?

Accepted Answer

The enzyme will lack catalytic activity.

Question 16

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

Accepted Answer

It decreases $$V_{max}$$ but does not affect $$K_m.$$

Question 17

Which of the following is a real-world example of an enzyme that is not a protein?

Accepted Answer

Ribonuclease P, which is an RNA molecule with catalytic activity

Question 18

Which of the following best describes the induced-fit model of enzyme action?

Accepted Answer

The enzyme changes conformation upon substrate binding, optimizing interactions for catalysis.

Question 19

Which of the following scenarios best illustrates substrate-level regulation?

Accepted Answer

An increase in substrate concentration leads to an increased reaction rate.

Question 20

Which of the following is true regarding the effect of pH on enzyme activity?

Accepted Answer

Enzyme activity is highest at its optimal pH, which varies depending on the enzyme.

Enzymes: The Catalysts of Life – Comprehensive Study Notes

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