Question 1

Which of the following best describes the function of an enzyme's active site?

Accepted Answer

It is the region where substrate molecules bind and undergo a chemical reaction.

Question 2

Standard conditions for calculating $$\Delta G^\circ ($$standard free energy change) include which of the following?

Accepted Answer

1 M concentration of reactants and products, 25$$^\circC$$, 1 atm pressure, pH 7

Question 3

Which equation correctly relates the standard free energy change to the equilibrium constant $$K_{eq}$$?

Accepted Answer

$$\Delta G^\circ = -RT \ln K_{eq}$$

Question 4

Hexokinase has a $$K_m of 1.5 mM $$for D-fructose and 0.05 mM for D-glucose. What does this suggest about the enzyme's substrate specificity?

Accepted Answer

Hexokinase has a higher affinity for D-glucose than D-fructose.

Question 5

What is the primary purpose of irreversible enzyme inhibitors in medicine?

Accepted Answer

To permanently inactivate enzymes, often for therapeutic purposes such as antibiotics or chemotherapy.

Question 6

Which of the following is true regarding the effect of a competitive inhibitor on $$V_{max}$$ and $$K_m$$?

Accepted Answer

$$V_{max}$$ remains unchanged, $$K_m$$ increases.

Question 7

Given the following Michaelis-Menten equation, what does $$V_{max}$$ represent?

$$V = \frac{V_{max}[S]}{K_m + [S]}$$

Accepted Answer

The maximum velocity achieved by the enzyme when substrate concentration is saturating.

Question 8

A mutation in holo-HasA reduces its activity compared to the wild-type enzyme. Based on the provided figure, which mutation has the greatest negative effect on enzyme activity?

Accepted Answer

Holo-HasA, H32A, Y75A, denatured

Question 9

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

Accepted Answer

$$V_{max}$$ decreases, $$K_m$$ remains unchanged.

Question 10

What conformational change occurs when ATP binds to myosin, and what is the rate-limiting step in the myosin ATPase cycle?

Accepted Answer

ATP binding causes myosin to release from actin; the rate-limiting step is the release of ADP and Pi.

Question 11

Which of the following graphs best represents the effect of a competitive inhibitor on enzyme kinetics?

Accepted Answer

A graph where $$V_{max} is $$unchanged but $$K_m$$ increases (the curve shifts right).

Question 12

If an enzyme has a low $$K_m$$ value for a substrate, what does this indicate?

Accepted Answer

The enzyme has a high affinity for the substrate.

Question 13

Which of the following is a typical use for irreversible inhibitors in clinical settings?

Accepted Answer

Antibiotics that target bacterial enzymes.

Question 14

A patient is given a drug that acts as a noncompetitive inhibitor of an essential metabolic enzyme. What is the expected effect on the enzyme's $$V_{max}$$ and $$K_m$$?

Accepted Answer

$$V_{max}$$ decreases, $$K_m$$ remains unchanged.

Question 15

Which of the following statements about the Michaelis-Menten constant $$K_m is $$correct?

Accepted Answer

$$K_m is $$the substrate concentration at which the reaction rate is half of $$V_{max}.$$

Question 16

Which of the following is NOT a characteristic of an enzyme's active site?

Accepted Answer

It is always located at the N-terminus of the protein.

Question 17

Which of the following best describes the effect of a mutation that denatures holo-HasA, as shown in the provided figure?

Accepted Answer

The enzyme loses almost all activity compared to the wild-type.

Question 18

Which of the following is the correct formula for the Michaelis-Menten equation?

Accepted Answer

$$V = \frac{V_{max}[S]}{K_m + [S]}$$

Question 19

Which of the following statements about ATP binding to myosin is correct?

Accepted Answer

ATP binding causes myosin to release from actin, allowing muscle relaxation.

Enzyme Kinetics, Inhibition, and Protein Function: Study Notes

Study Guide - Practice Questions

Study Guide - Flashcards