Question 1

Which statement best describes how enzymes increase the rate of a chemical reaction?

Accepted Answer

They provide an alternative reaction pathway with a lower activation energy ($$\Delta G$$^{\ddagger}$$).

Question 2

Consider the decomposition of hydrogen peroxide ($$\mathrm{H_2O_2}) $$into water and oxygen. Which of the following best explains the effect of a catalyst on this reaction?

Accepted Answer

The catalyst lowers the activation free energy, increasing the reaction rate.

Question 3

Which of the following is true about the active site of an enzyme?

Accepted Answer

It is a small portion of the enzyme surface where the substrate binds via noncovalent interactions.

Question 4

Which model of enzyme-substrate binding suggests that the enzyme changes shape upon substrate binding to achieve a complementary fit?

Accepted Answer

Induced fit model

Question 5

An enzyme-catalyzed reaction follows Michaelis-Menten kinetics. What is the initial velocity ($$v_0) $$when substrate concentration $$[S] is $$much greater than $$K_m$$?

Accepted Answer

$$v_0 = V$$_{max}$$

Question 6

Which of the following best describes competitive inhibition?

Accepted Answer

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

Question 7

In a Lineweaver-Burk plot of $$\dfrac{1}{v}$$ versus $$\dfrac{1}{[S]}$$, what does the y-intercept represent?

Accepted Answer

$$\dfrac{1}{V_{max}}$$

Question 8

Which of the following is a consequence of non-competitive inhibition on enzyme kinetics?

Accepted Answer

It decreases $$V_{max}$$ without changing $$K_m.$$

Question 9

Which of the following equations represents the Michaelis-Menten equation for initial velocity ($$v_0) of an $$enzyme-catalyzed reaction?

Accepted Answer

$$v_0$$ = \dfrac{V_{max}[S]}{K_m + [S]}$$

Question 10

A patient is given a drug that acts as a competitive inhibitor for a key metabolic enzyme. Which of the following changes would you expect in the enzyme's kinetic parameters?

Accepted Answer

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

Question 11

Which of the following best explains why enzymes are typically much larger than synthetic catalysts?

Accepted Answer

The protein fold must be sufficiently stable to form a cleft and organize active-site residues.

Question 12

Which of the following is true regarding the specificity of enzyme-catalyzed reactions?

Accepted Answer

Enzymatic reactions typically proceed without undesired side reactions.

Question 13

If an enzyme-catalyzed reaction exhibits zero-order kinetics with respect to substrate concentration, what does this imply?

Accepted Answer

The enzyme is saturated with substrate and the rate is independent of substrate concentration.

Question 14

Which of the following is the correct definition of the turnover number ($$k_{cat}) $$for an enzyme?

Accepted Answer

The number of substrate molecules converted to product per enzyme molecule per unit time under saturating substrate conditions.

Question 15

Which of the following statements about irreversible inhibitors is correct?

Accepted Answer

They permanently inactivate the enzyme by forming covalent bonds.

Question 16

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

Accepted Answer

It is a Lineweaver-Burk plot; $$K_m$$ and $$V_{max}$$ can be determined from the slope and intercept.

Question 17

Which of the following is a key difference between competitive and non-competitive inhibition?

Accepted Answer

Competitive inhibitors increase $$K_m$$ but do not affect $$V_{max}$$, while non-competitive inhibitors decrease $$V_{max}$$ but do not affect $$K_m.$$

Question 18

Which of the following best describes the lock-and-key model of enzyme-substrate binding?

Accepted Answer

The substrate binds to a region of the enzyme with a complementary shape.

Question 19

Which of the following is the correct rate law for a reaction where the rate depends on the concentration of two reactants, $$A$$ and $$B$$, and is second order overall?

Accepted Answer

$$	ext{Rate} = k[A][B]$$

Enzyme Catalysis and Kinetics: Structured Study Notes Ch 6

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