Question 1

Which of the following best describes the role of serine 195 in the catalytic mechanism of chymotrypsin?

Accepted Answer

It forms a covalent intermediate with the substrate, acting as a nucleophile.

Question 2

Which environmental factor would most likely decrease the rate of an enzyme-catalyzed reaction by denaturing the enzyme?

Accepted Answer

Raising the temperature significantly above optimal

Question 3

A Lineweaver-Burk plot of enzyme kinetics in the presence of a competitive inhibitor will show:

Accepted Answer

No change in $$V_{max}$$ and an increase in $$K_m$$

Question 4

Penicillin inhibits bacterial cell wall synthesis by targeting which enzyme?

Accepted Answer

Transpeptidase

Question 5

Which statement best explains why affinity labels are useful in studying enzyme active sites?

Accepted Answer

They covalently modify specific residues, mimicking the enzyme's natural substrate.

Question 6

In the Michaelis-Menten model, what is the effect of a pure noncompetitive inhibitor on $$V_{max}$$ and $$K_m$$?

Accepted Answer

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

Question 7

Which of the following is a general acid-base catalyst in the chymotrypsin active site?

Accepted Answer

Histidine 57

Question 8

A group-specific reagent irreversibly inhibits enzymes by:

Accepted Answer

Reacting with specific side chains to form covalent bonds

Question 9

Which of the following best describes the substrate selectivity of chymotrypsin?

Accepted Answer

It cleaves peptide bonds on the carboxyl side of aromatic and hydrophobic residues.

Question 10

Which of the following equations represents the Michaelis-Menten equation for enzyme kinetics?

Accepted Answer

$$v = \frac{V_{max}[S]}{K_m + [S]}$$

Question 11

Which type of inhibition can be overcome by increasing substrate concentration?

Accepted Answer

Competitive inhibition

Question 12

A patient is exposed to sarin, a nerve agent that irreversibly inhibits acetylcholinesterase. What type of inhibition is this?

Accepted Answer

Irreversible inhibition

Question 13

Which of the following best describes the effect of an uncompetitive inhibitor on enzyme kinetics?

Accepted Answer

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

Question 14

Which of the following is NOT a catalytic strategy commonly used by enzymes?

Accepted Answer

Hydrolysis by water alone without enzyme involvement

Question 15

Why is the $$eta-$$lactam ring of penicillin crucial for its antibiotic activity?

Accepted Answer

It mimics the transition state of the transpeptidase reaction, allowing penicillin to bind and inactivate the enzyme.

Question 16

Which of the following statements about reversible inhibitors is TRUE?

Accepted Answer

They can be removed by dialysis or dilution.

Question 17

A researcher uses TPCK to study chymotrypsin. What is the primary reason TPCK is effective as an affinity label?

Accepted Answer

It is structurally similar to the enzyme's natural substrate and covalently modifies a specific histidine residue.

Question 18

Which of the following best explains the effect of pH on enzyme activity?

Accepted Answer

Extreme pH values can denature the enzyme and reduce activity.

Question 19

Which of the following is a consequence of irreversible inhibition?

Accepted Answer

The enzyme is permanently inactivated due to covalent modification.

Question 20

Which of the following best describes the transition state in enzyme-catalyzed reactions?

Accepted Answer

It is a high-energy, short-lived intermediate that enzymes stabilize to accelerate the reaction.

Enzyme Catalysis: Strategies, Kinetics, and Inhibition

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