Question 1

Which of the following statements best describes the role of an enzyme in a biochemical reaction?

Accepted Answer

An enzyme increases the rate of a reaction by lowering the activation energy ($$\Delta G^\circ\ddagger) $$required to reach the transition state.

Question 2

A patient with lactose intolerance is unable to digest lactose due to a deficiency in which enzyme, and what are the products of the reaction catalyzed by this enzyme?

Accepted Answer

Lactase; products are glucose and galactose.

Question 3

Which equation correctly represents the Michaelis-Menten equation for an enzyme-catalyzed reaction?

Accepted Answer

$$v = \dfrac{V_{max}[S]}{K_M + [S]}$$

Question 4

In the context of enzyme kinetics, what does the parameter $$K_M$$ represent when $$k_{cat} \ll k_{-1}$$?

Accepted Answer

$$K_M$$ approximates the dissociation constant ($$K_d) $$for the enzyme-substrate complex.

Question 5

A Lineweaver-Burk plot is used to analyze enzyme kinetics. What is plotted on the x- and y-axes, and what does the y-intercept represent?

Accepted Answer

x-axis: $$1/[S]$$, y-axis: $$1/v$$, y-intercept: $$1/V_{max}$$

Question 6

Which of the following best explains why increasing temperature generally increases the rate of an enzyme-catalyzed reaction (up to a point)?

Accepted Answer

Higher temperature increases the number of molecules with sufficient energy to overcome the activation energy barrier ($$\Delta G^\circ\ddagger).$$

Question 7

A mutation in the Lamin A gene leads to Hutchinson-Gilford progeria syndrome (HGPS). Which therapeutic approach has been shown to extend lifespan in progeria mice?

Accepted Answer

Telomerase therapy

Question 8

Which of the following is a correct expression for the rate of a second-order reaction with respect to substrate $$A$$?

Accepted Answer

$$v = k[A]^2$$

Question 9

In a multisubstrate enzyme reaction following a ping-pong mechanism, what is a distinguishing feature compared to sequential mechanisms?

Accepted Answer

One product is released before the second substrate binds.

Question 10

Which of the following best describes the effect of an enzyme on the transition state of a reaction?

Accepted Answer

The enzyme stabilizes the transition state, lowering $$\Delta G^\circ\ddagger$$ and increasing the reaction rate.

Question 11

A patient with chronic creatine kinase (CK) deficiency is at increased risk for which of the following conditions, especially under high cardiac demand?

Accepted Answer

Congestive heart failure

Question 12

Given the Arrhenius equation $$k = Ae$$^{-\Delta G^\circ\ddagger/RT}$$, which of the following changes will increase the rate constant k$?

Accepted Answer

Decrease $$\Delta G^\circ\ddagger$$

Question 13

Which of the following is true regarding the maximum velocity ($$V_{max}) of an $$enzyme-catalyzed reaction?

Accepted Answer

$$V_{max} is $$reached when all enzyme active sites are saturated with substrate.

Question 14

Which of the following best describes the rate enhancement provided by an enzyme?

Accepted Answer

It is the ratio of the catalyzed rate constant ($$k_{cat}) to $$the uncatalyzed rate constant ($$k_{uncat}).$$

Question 15

Which of the following is a key assumption of the Michaelis-Menten model for enzyme kinetics?

Accepted Answer

A steady-state concentration of the enzyme-substrate complex is rapidly achieved.

Question 16

Which of the following is a correct interpretation of a Lineweaver-Burk plot for a ping-pong mechanism?

Accepted Answer

Parallel lines are observed when varying the concentration of one substrate at different fixed concentrations of the other.

Question 17

Which of the following is a real-world example of an enzyme-catalyzed reaction relevant to human health?

Accepted Answer

Lactase hydrolyzing lactose into glucose and galactose in the small intestine.

Question 18

Which of the following statements about $$k_{cat} is $$correct?

Accepted Answer

$$k_{cat} is $$the turnover number, representing the number of substrate molecules converted to product per enzyme molecule per second.

Question 19

Which of the following best explains why enzyme-catalyzed reactions plateau at high substrate concentrations?

Accepted Answer

All enzyme active sites are occupied, so increasing substrate concentration further does not increase the rate.

Enzyme Kinetics: Principles, Mechanisms, and Applications

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