Question 1

Which of the following best describes the role of enzymes in cellular chemical reactions?

Accepted Answer

Enzymes decrease the activation energy, thereby increasing the rate of reactions.

Question 2

Given the reaction $$\mathrm{H_2$ + I_2$ \rightarrow 2HI}$$, which statement is correct regarding the spontaneity and direction of the reaction?

Accepted Answer

The reaction is exergonic and will proceed spontaneously to the right.

Question 3

Which of the following equations represents the Michaelis-Menten equation for enzyme kinetics?

Accepted Answer

$$V_0$$ = \dfrac{V_{max}[S]}{K_m + [S]}$$

Question 4

What does the value of $$K_m$$ indicate about an enzyme's affinity for its substrate?

Accepted Answer

A low $$K_m$$ means the enzyme binds the substrate tightly.

Question 5

Which of the following statements about competitive inhibition is correct?

Accepted Answer

Competitive inhibitors bind to the active site and can be overcome by increasing substrate concentration.

Question 6

A non-competitive inhibitor affects enzyme kinetics by:

Accepted Answer

Decreasing $$V_{max}$$ and leaving $$K_m$$ unchanged.

Question 7

Which of the following best explains why enzymes are specific for their substrates?

Accepted Answer

Enzymes have active sites with shapes and chemical properties complementary to their substrates.

Question 8

If an enzyme has a turnover number ($$k_{cat}) of 600$$,000 s$$^{-1}$$, what does this mean?

Accepted Answer

Each enzyme molecule converts 600,000 substrate molecules to product per second.

Question 9

Which of the following is a real-life example of a competitive inhibitor used as a drug?

Accepted Answer

Lovastatin, which inhibits HMG-CoA reductase in cholesterol biosynthesis.

Question 10

In the context of enzyme regulation, what is feedback inhibition?

Accepted Answer

The end product of a metabolic pathway inhibits an enzyme involved in an earlier step.

Question 11

Which of the following best describes the induced fit theory of enzyme action?

Accepted Answer

The enzyme changes shape upon substrate binding to better fit the substrate.

Question 12

Which of the following is true about the plateau observed in the $$V_0 vs$$. $$[S]$$ graph for enzyme-catalyzed reactions?

Accepted Answer

It occurs because all enzyme active sites are saturated with substrate.

Question 13

Which of the following equations correctly defines $$K_m in $$terms of rate constants?

Accepted Answer

$$K_m = \dfrac{k_2$ + k_3$}{k_1$}$$

Question 14

A mutation in an enzyme decreases its $$k_{cat}$$ but does not affect $$K_m. $$What is the most likely effect on the enzyme's function?

Accepted Answer

The enzyme binds substrate normally but converts it to product more slowly.

Question 15

Which of the following statements about allosteric inhibition is correct?

Accepted Answer

Allosteric inhibitors bind to a site other than the active site and can affect $$K_m$$, $$V_{max}$$, or both.

Question 16

Which of the following best explains why platinum can catalyze both cis- and trans-fumarate reactions, while enzymes cannot?

Accepted Answer

Platinum is a non-specific inorganic catalyst, while enzymes are highly specific for their substrates.

Question 17

If the initial velocity ($$V_0) of an $$enzyme-catalyzed reaction is measured at various substrate concentrations and plotted, what does the substrate concentration at which $$V_0$$ = \dfrac{V_{max}}{2}$$ represent?

Accepted Answer

The Michaelis constant ($$K_m)$$

Question 18

Which of the following is NOT a way that enzymes accelerate chemical reactions?

Accepted Answer

By increasing the activation energy required to reach the transition state.

Question 19

In a metabolic pathway, why is the first committed step often regulated by feedback inhibition?

Accepted Answer

To prevent the unnecessary accumulation of intermediates and conserve resources.

Enzyme Kinetics, Inhibition, and Regulation: Biochemistry Study Notes

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