Question 1

Which statement best describes the difference between the lock-and-key model and the induced fit model of enzyme specificity?

Accepted Answer

The lock-and-key model proposes that the enzyme and substrate have complementary shapes that fit exactly, while the induced fit model proposes that the enzyme undergoes a conformational change upon substrate binding.

Question 2

On a reaction coordinate diagram, what effect does the presence of an enzyme have on the activation energy ($$E_a) $$and the free energy change ($$\Delta G) of a $$biochemical reaction?

Accepted Answer

The enzyme decreases $$E_a$$ but does not change $$\Delta G.$$

Question 3

Which of the following is NOT a function of a cofactor in enzymatic reactions?

Accepted Answer

Providing a source of energy for the reaction.

Question 4

Which step in the enzyme-catalyzed reaction pathway is most directly affected by the presence of a transition state analog inhibitor?

Accepted Answer

Transition state stabilization.

Question 5

Which of the following best explains how metal ions can stabilize the transition state in enzyme-catalyzed reactions?

Accepted Answer

By neutralizing negative charges that develop during the reaction.

Question 6

Given the Michaelis-Menten equation $$v = \frac{V_{max}[S]}{K_m + [S]}$$, what happens to the initial reaction velocity ($$v) $$when substrate concentration $$[S] is $$much greater than $$K_m$$?

Accepted Answer

The reaction velocity approaches $$V_{max}.$$

Question 7

Which of the following changes would increase the value of $$K_m$$ for an enzyme-catalyzed reaction?

Accepted Answer

Introducing a competitive inhibitor.

Question 8

A patient is treated with a drug that acts as a non-competitive inhibitor of an enzyme. Which of the following best describes the effect on $$V_{max}$$ and $$K_m$$?

Accepted Answer

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

Question 9

Which scenario would most likely result in uncompetitive inhibition of an enzyme?

Accepted Answer

The inhibitor binds only to the enzyme-substrate complex.

Question 10

An enzyme has a $$K_m of 5 mM $$and a $$V_{max} of 100$$ $$\mu$$mol/min. If the substrate concentration is 5 mM, what is the initial velocity ($$v) $$according to the Michaelis-Menten equation?

Accepted Answer

$$v = 50\ \mu$$mol/min

Question 11

Which of the following statements about competitive inhibition is correct?

Accepted Answer

Competitive inhibitors bind to the active site and increase $$K_m$$ without affecting $$V_{max}.$$

Question 12

Which of the following is a real-world example of a cofactor required for enzyme activity?

Accepted Answer

Magnesium ion ($$Mg^{2+}) $$required by DNA polymerase.

Question 13

If an enzyme-catalyzed reaction is performed at a substrate concentration much lower than $$K_m$$, what is the approximate relationship between initial velocity ($$v) $$and substrate concentration ($$[S]$$)?

Accepted Answer

$$v is $$directly proportional to $$[S].$$

Question 14

Which of the following best describes the effect of a drop in enzyme concentration on $$K_m$$ and $$V_{max}$$?

Accepted Answer

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

Question 15

Which of the following is a key feature of acid-base catalysis in enzyme mechanisms?

Accepted Answer

Proton donation or acceptance by amino acid side chains in the active site.

Question 16

Which of the following statements about the transition state in enzyme-catalyzed reactions is correct?

Accepted Answer

The transition state is stabilized by interactions with the enzyme's active site.

Question 17

Which parameter is most useful for comparing the catalytic efficiency of different enzymes?

Accepted Answer

$$\frac{V_{max}}{K_m}$$

Question 18

A mutation in an enzyme reduces its ability to stabilize the transition state. What is the most likely effect on the reaction rate?

Accepted Answer

The reaction rate will decrease.

Question 19

Which of the following best describes the effect of uncompetitive inhibition on $$K_m$$ and $$V_{max}$$?

Accepted Answer

Both $$K_m$$ and $$V_{max}$$ decrease.

Enzyme Kinetics and Catalysis: Study Guide Notes- Module 4

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