Question 1

Which statement best describes how enzymes accelerate chemical reactions?

Accepted Answer

Enzymes lower the activation energy by binding the transition state better than the substrate.

Question 2

Which of the following is TRUE regarding the Michaelis-Menten constant $$K_m$$?

Accepted Answer

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

Question 3

A competitive inhibitor affects enzyme kinetics by:

Accepted Answer

Increasing $$K_m$$ but not changing $$V_{max}.$$

Question 4

Which equation represents the Michaelis-Menten relationship between initial velocity ($$v$$), substrate concentration ($$[S]$$), maximal velocity ($$V_{max}$$), and $$K_m$$?

Accepted Answer

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

Question 5

Which of the following statements about $$V_{max} is $$correct?

Accepted Answer

$$V_{max} is $$the velocity achieved when all enzyme molecules are saturated with substrate.

Question 6

The turnover number ($$k_{cat}) of an $$enzyme is defined as:

Accepted Answer

The number of substrate molecules converted to product per enzyme molecule per unit time when the enzyme is saturated with substrate.

Question 7

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

Accepted Answer

Penicillin inhibiting bacterial transpeptidase.

Question 8

In a Lineweaver-Burk plot, which of the following changes would you expect in the presence of a pure noncompetitive inhibitor?

Accepted Answer

The $$y-$$intercept increases, but the $$x-$$intercept remains unchanged.

Question 9

Which enzyme class catalyzes the conversion of ethanol to acetaldehyde?

Accepted Answer

Oxidoreductase

Question 10

A patient is treated with nevirapine, a non-nucleoside reverse transcriptase inhibitor. What is the most likely effect on HIV replication?

Accepted Answer

Inhibition of viral RNA to DNA conversion, reducing viral replication.

Question 11

Which of the following best describes the effect of pH on enzyme activity?

Accepted Answer

Enzyme activity is highest at the enzyme's optimal pH and decreases at pH values above or below this optimum.

Question 12

Which of the following is the correct Lineweaver-Burk equation for enzyme kinetics?

Accepted Answer

$$\frac{1}{v} = \frac{K_m}{V_{max}} \cdot \frac{1}{[S]} + \frac{1}{V_{max}}$$

Question 13

Which of the following statements about enzyme specificity is correct?

Accepted Answer

Enzyme specificity is controlled by the structure and fit of the substrate with the enzyme's active site.

Question 14

Which of the following is a competitive inhibitor of succinate dehydrogenase?

Accepted Answer

Malonate

Question 15

If an enzyme has a very small $$K_m$$, what does this indicate about the enzyme-substrate interaction?

Accepted Answer

The enzyme binds the substrate tightly.

Question 16

Which of the following is the best measure of catalytic efficiency for an enzyme?

Accepted Answer

$$\frac{k_{cat}}{K_m}$$

Question 17

Which of the following statements about noncompetitive inhibition is correct?

Accepted Answer

Noncompetitive inhibitors decrease $$V_{max}$$ but do not change $$K_m.$$

Question 18

Which of the following is NOT a major class of enzyme?

Accepted Answer

Polymerase

Question 19

A researcher measures the initial velocity of an enzyme-catalyzed reaction at various substrate concentrations and plots $$\frac{1}{v}$$ versus $$\frac{1}{[S]}. $$What type of plot is this and what information can be obtained from it?

Accepted Answer

Lineweaver-Burk plot; $$K_m$$ and $$V_{max}$$ can be determined from the slope and intercepts.

Enzymes: Biological Catalysts and Enzyme Kinetics

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