Question 1

Which of the following best describes competitive inhibition in enzyme kinetics?

Accepted Answer

The inhibitor competes with the substrate for binding at the active site, preventing substrate access.

Question 2

What effect does a competitive inhibitor have on the apparent $K_m$ and $V_{max}$ of an enzyme-catalyzed reaction?

Accepted Answer

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

Question 3

In a Lineweaver-Burk plot, how does the presence of a competitive inhibitor affect the slope and y-intercept?

Accepted Answer

Slope increases, y-intercept remains the same.

Question 4

Given the Michaelis-Menten equation $v = \frac{V_{max}[S]}{K_m + [S]}$, what happens to the reaction rate at low substrate concentration $[S]$ in the presence of a competitive inhibitor?

Accepted Answer

The reaction rate decreases because $K_m$ is increased.

Question 5

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

Accepted Answer

Methotrexate competing with folic acid for dihydrofolate reductase.

Question 6

If the $K_m$ of an enzyme for its substrate is 10 mM in the absence of inhibitor, and 20 mM in the presence of a competitive inhibitor, what is the effect of the inhibitor?

Accepted Answer

It decreases the enzyme's affinity for the substrate.

Question 7

Which statement about competitive inhibitors is FALSE?

Accepted Answer

They decrease the maximum velocity ($V_{max}$) of the reaction.

Question 8

A patient is given a drug that acts as a competitive inhibitor for an essential enzyme. What would be the most effective way to overcome the inhibition?

Accepted Answer

Increase the concentration of the substrate.

Question 9

Which plot would show a steeper slope in the presence of a competitive inhibitor?

Accepted Answer

Lineweaver-Burk plot of $\frac{1}{v}$ vs $\frac{1}{[S]}$

Question 10

If $K_m$ in the absence of inhibitor is 5 mM and in the presence of inhibitor is 10 mM, what is the fold increase in $K_m$ due to the inhibitor?

Accepted Answer

2-fold

Question 11

Which of the following is NOT a characteristic of competitive inhibition?

Accepted Answer

Inhibitor decreases $V_{max}$.

Question 12

How does competitive inhibition affect the free enzyme concentration in a reaction mixture?

Accepted Answer

It decreases the free enzyme concentration.

Question 13

Which equation correctly represents the effect of a competitive inhibitor on the Michaelis-Menten constant?

Accepted Answer

$K_m^{app} = K_m \left(1 + \frac{[I]}{K_i}\right)$

Question 14

A competitive inhibitor has a $K_i$ of 10 nM. If the inhibitor concentration $[I]$ is 10 nM, what is the factor by which $K_m$ increases?

Accepted Answer

2-fold

Question 15

Which of the following would NOT be expected if a competitive inhibitor is present in an enzyme assay?

Accepted Answer

The $V_{max}$ of the reaction is reduced.

Question 16

In the absence of inhibitor, $K_m = 5$ mM. In the presence of inhibitor, $K_m = 10$ mM. What is the value of $K_i$ if $[I] = 5$ mM?

Accepted Answer

$K_i = 5$ mM

Question 17

Which scenario would result in the greatest inhibition by a competitive inhibitor?

Accepted Answer

Low substrate concentration, high inhibitor concentration.

Question 18

What is the primary difference between competitive and noncompetitive inhibition?

Accepted Answer

Competitive inhibitors bind to the active site, while noncompetitive inhibitors bind elsewhere.

Question 19

If an enzyme reaction is measured in the presence and absence of a competitive inhibitor, which parameter will remain unchanged?

Accepted Answer

$V_{max}$

Competitive Inhibition in Enzyme Kinetics

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