Question 1

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

Accepted Answer

An enzyme decreases the overall activation energy, thereby increasing the reaction rate.

Question 2

Given the following equilibrium constant $$K_{eq} = 10$$^{-4}$$, what is the standard Gibbs free energy change $$\Delta G^\circ$$ for the reaction? Use the table provided in the study materials.

Accepted Answer

$$\Delta G^\circ = 22.8 kJ/$$mol

Question 3

Which class of enzyme catalyzes the transfer of functional groups from one molecule to another?

Accepted Answer

Transferases

Question 4

A researcher observes that an enzyme-catalyzed reaction proceeds faster than the uncatalyzed reaction. Which of the following is NOT a reason for this increased rate?

Accepted Answer

Increase in the overall free energy change $$\Delta G$$

Question 5

Which amino acid is LEAST likely to participate in general acid-base catalysis?

Accepted Answer

Valine

Question 6

In the context of enzyme kinetics, what does the Michaelis constant $$K_m$$ represent?

Accepted Answer

The substrate concentration at which the reaction rate is half-maximal ($$V_{max}/2)$$

Question 7

Which of the following is TRUE regarding the relationship between $$K_{eq}$$ and $$\Delta G$$?

Accepted Answer

When $$K_{eq} is $$small, $$\Delta G is $$positive.

Question 8

Which of the following best describes the 'induced fit' model of enzyme action?

Accepted Answer

The enzyme changes shape upon substrate binding to better stabilize the transition state.

Question 9

Which of the following is a feature of covalent catalysis?

Accepted Answer

Formation of a transient covalent bond between enzyme and substrate

Question 10

A Lineweaver-Burk plot is used to determine which two key kinetic parameters of an enzyme-catalyzed reaction?

Accepted Answer

$$K_m$$ and $$V_{max}$$

Question 11

Which of the following amino acids is most likely to act as a general base in enzyme catalysis?

Accepted Answer

Lysine

Question 12

Which enzyme class is responsible for catalyzing the hydrolysis of chemical bonds?

Accepted Answer

Hydrolases

Question 13

If an enzyme has a $$V_{max} of 100$$ $$\mu$$mol/min and a $$K_m of 10$$ $$\muM$$, what is the initial velocity $$v_0$$ when the substrate concentration $$[S] is 10$$ $$\muM$$? Use the Michaelis-Menten equation: $$v_0$$ = \frac{V_{max}[S]}{K_m + [S]}$$.

Accepted Answer

50 $$\mu$$mol/min

Question 14

Which of the following is NOT a function of enzymes in catalyzing reactions?

Accepted Answer

Increasing the entropy of solution

Question 15

Which of the following best describes the difference between specific acid-base catalysis and general acid-base catalysis?

Accepted Answer

Specific acid-base catalysis uses only H$$^+ or OH$^-$$ ions present in water, while general acid-base catalysis is mediated by weak acids or bases other than water.

Question 16

Which of the following is the correct formula for the Michaelis-Menten constant $$K_m$$?

Accepted Answer

$$K_m = [S] at$$ $$V_{max}/2$$

Question 17

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

Accepted Answer

$$k_{cat} = \frac{V_{max}}{[E]_{total}}$$

Question 18

Which of the following statements about the dissociation constant $$K_d is $$correct?

Accepted Answer

$$K_d is a $$measure of how readily a molecule dissociates into smaller components.

Question 19

Which amino acid is most likely to form a transient covalent bond with a substrate during covalent catalysis?

Accepted Answer

Serine

Enzyme Catalysis: Chemical Essence, Mechanisms, and Kinetics

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