Question 1

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

Accepted Answer

It increases $$K_M$$ and leaves $$V_{max}$$ unchanged.

Question 2

A patient overdoses on an organophosphate pesticide, which irreversibly inhibits acetylcholinesterase. Which of the following best explains why this inhibition is considered irreversible?

Accepted Answer

The inhibitor binds covalently to the enzyme, permanently inactivating it.

Question 3

Which of the following equations correctly represents the dissociation constant ($$K_I) $$for an inhibitor binding to the free enzyme?

Accepted Answer

$$K_I = \frac{[E][I]}{[EI]}$$

Question 4

Which of the following statements about uncompetitive inhibition is TRUE?

Accepted Answer

The inhibitor binds only to the enzyme-substrate complex.

Question 5

A Lineweaver-Burk plot of an enzyme-catalyzed reaction in the presence of a noncompetitive inhibitor will show:

Accepted Answer

Lines intersecting at the x-axis.

Question 6

Which of the following best describes the mechanism of action of aspirin (acetylsalicylic acid) on cyclooxygenase enzymes?

Accepted Answer

Aspirin irreversibly inhibits cyclooxygenase by covalently modifying a serine residue.

Question 7

Which of the following is a characteristic of mixed inhibition?

Accepted Answer

The inhibitor binds to both the free enzyme and the enzyme-substrate complex, but with different affinities.

Question 8

Statins, such as simvastatin and pravastatin, are used to lower cholesterol by inhibiting HMG-CoA reductase. What type of inhibition do statins exhibit?

Accepted Answer

Competitive inhibition

Question 9

In the context of enzyme inhibition, what does the term 'suicide inhibition' refer to?

Accepted Answer

An inhibitor that binds covalently to the enzyme after being processed by the enzyme, leading to irreversible inactivation.

Question 10

Which of the following changes would you expect to see in the presence of an uncompetitive inhibitor?

Accepted Answer

$$V_{max}$$ decreases and $$K_M$$ decreases.

Question 11

A new drug is found to bind noncovalently with extremely high affinity ($$K_d \u003c 10$$^{-8}$$ M) to an enzyme. Which type of inhibition is this most likely to represent?

Accepted Answer

Reversible inhibition

Question 12

Which of the following best explains why competitive inhibitors often resemble the transition state of the substrate?

Accepted Answer

Because enzymes bind the transition state more tightly than the substrate, so mimicking it increases inhibitor affinity.

Question 13

Which of the following is TRUE regarding the effect of a noncompetitive inhibitor on $$K_M$$ and $$V_{max}$$?

Accepted Answer

$$K_M$$ remains unchanged and $$V_{max}$$ decreases.

Question 14

A researcher observes that increasing substrate concentration does not overcome the inhibition of an enzyme by a certain compound. Which type of inhibition is most likely occurring?

Accepted Answer

Uncompetitive inhibition

Question 15

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

Accepted Answer

$$V_{max}$$ decreases and $$K_M$$ may increase or decrease depending on the relative affinities for E and ES.

Question 16

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

Accepted Answer

Aspirin inhibition of cyclooxygenase

Question 17

If an inhibitor binds to both the free enzyme and the enzyme-substrate complex with equal affinity, what type of inhibition is this?

Accepted Answer

Noncompetitive inhibition

Question 18

Which of the following best describes the effect of a competitive inhibitor on a Lineweaver-Burk plot?

Accepted Answer

The lines for different inhibitor concentrations intersect at the y-axis.

Question 19

A plant herbicide acts as an uncompetitive inhibitor of an enzyme in the shikimate pathway. Which of the following changes would you expect in the presence of this herbicide?

Accepted Answer

$$V_{max}$$ and $$K_M$$ both decrease.

Question 20

Which of the following statements about reversible enzyme inhibition is CORRECT?

Accepted Answer

Reversible inhibitors can be displaced by high concentrations of substrate.

Enzyme Inhibition: Mechanisms and Types in Biochemistry

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