Question 1

Which statement best describes the role of enzymes in biochemical reactions?

Accepted Answer

Enzymes lower the activation energy, thereby increasing the rate of reaction.

Question 2

Apoenzymes are:

Accepted Answer

Enzymes that lack their required cofactors.

Question 3

Which of the following is TRUE regarding the Michaelis-Menten constant ($$K_m$$)?

Accepted Answer

$$K_m is $$the substrate concentration at which the reaction rate is half of $$V_{max}.$$

Question 4

Which equation correctly represents the initial velocity ($$V_0) of an $$enzyme-catalyzed reaction according to Michaelis-Menten kinetics?

Accepted Answer

$$V_0$$ = \dfrac{V_{max}[S]}{K_m + [S]}$$

Question 5

A competitive inhibitor affects enzyme kinetics by:

Accepted Answer

Increasing $$K_m$$ but not affecting $$V_{max}$$

Question 6

Which of the following is a characteristic of acid-base catalysis?

Accepted Answer

It is highly sensitive to pH and often uses amino acids like Glu, Asp, and His as proton donors or acceptors.

Question 7

The rate-limiting step in a multistep enzymatic reaction is:

Accepted Answer

The step with the highest activation energy.

Question 8

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

Accepted Answer

The enzyme provides binding energy that helps the substrate reach the transition state.

Question 9

Which of the following is TRUE about $$k_{cat} in $$enzyme kinetics?

Accepted Answer

$$k_{cat}$$ represents the turnover number, or the number of substrate molecules converted to product per enzyme per unit time.

Question 10

Which of the following mechanisms is used by chymotrypsin to cleave peptide bonds?

Accepted Answer

A catalytic triad involving Ser195, His57, and Asp102 that facilitates covalent catalysis.

Question 11

Which of the following is a feature of feedback inhibition in metabolic pathways?

Accepted Answer

The final product of the pathway allosterically inhibits an enzyme early in the pathway.

Question 12

Which of the following is TRUE about irreversible inhibition?

Accepted Answer

It often involves covalent modification of the enzyme, permanently inactivating it.

Question 13

Which equation relates the equilibrium constant ($$K_{eq}) to $$the standard free energy change ($$\Delta G^\circ$$)?

Accepted Answer

$$\Delta G^\circ = RT \ln K_{eq}$$

Question 14

Which of the following statements about enzyme specificity is correct?

Accepted Answer

Binding energy derived from multiple sources contributes to enzyme specificity.

Question 15

Which of the following is TRUE about allosteric regulation of enzymes?

Accepted Answer

Allosteric enzymes can be regulated by both positive and negative effectors.

Question 16

Which of the following is a correct description of a zymogen?

Accepted Answer

A zymogen is an inactive precursor of an enzyme that requires proteolytic cleavage for activation.

Question 17

Which of the following is the correct unit for a second order rate constant ($$k) in $$enzyme kinetics?

Accepted Answer

$$M^{-1}s$$^{-1}$

Question 18

Which of the following statements about the relationship between reaction rate and activation energy ($$\Delta G$$^{\ddagger}$$) is correct?

Accepted Answer

The relationship is inverse and exponential.

Question 19

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

Accepted Answer

Botulinum toxin cleaving SNAP-25, preventing neurotransmitter release.

Question 20

Which of the following is TRUE regarding phosphorylation as a regulatory mechanism?

Accepted Answer

Phosphorylation can either activate or inactivate enzymes depending on the site and context.

Enzymes: Structure, Function, and Kinetics (Chapter 6 Study Notes)

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