Question 1

Which of the following best describes how a catalyst affects a chemical reaction?

Accepted Answer

It increases the rate of the reaction by lowering the activation energy without being consumed in the process.

Question 2

Which enzyme class is responsible for transferring functional groups from one molecule to another?

Accepted Answer

Transferases

Question 3

A patient is exposed to a nerve toxin that covalently binds to the active site serine of acetylcholinesterase. What type of enzyme inhibition is this?

Accepted Answer

Irreversible inhibition

Question 4

Which of the following statements about the induced fit model of enzyme-substrate interaction is correct?

Accepted Answer

The enzyme undergoes a conformational change to better fit the substrate upon binding.

Question 5

Which of the following mechanisms is NOT a way enzymes achieve rate acceleration?

Accepted Answer

Increasing the activation energy of the reaction

Question 6

A competitive inhibitor affects enzyme kinetics by:

Accepted Answer

Binding to the active site and increasing the apparent $$K_m$$ without affecting $$V_{max}$$

Question 7

Which of the following best describes the role of metal ions such as Zn$$^{2+} in $$enzymes?

Accepted Answer

They help bind substrates or stabilize negative charges during catalysis.

Question 8

Which of the following is an example of reversible covalent modification regulating enzyme activity?

Accepted Answer

Phosphorylation by kinases and dephosphorylation by phosphatases

Question 9

Which statement about allosteric enzymes is TRUE?

Accepted Answer

They are usually multisubunit proteins that change conformation upon effector binding.

Question 10

Which of the following best describes feedback inhibition in metabolic pathways?

Accepted Answer

The end product of a pathway inhibits an enzyme at a committed step, preventing overproduction.

Question 11

Which of the following is TRUE about ribozymes?

Accepted Answer

They are RNA molecules that catalyze chemical reactions.

Question 12

A researcher observes that an inhibitor binds only to the ES complex and not to the free enzyme. What type of inhibition is this?

Accepted Answer

Uncompetitive inhibition

Question 13

Which vitamin is a precursor for a coenzyme involved in oxidation-reduction reactions?

Accepted Answer

Riboflavin (vitamin B$$_2)$$

Question 14

Which of the following is a characteristic of noncompetitive (mixed) inhibition?

Accepted Answer

The inhibitor can bind to both the free enzyme and the ES complex at a site different from the active site.

Question 15

Which of the following is NOT a function of coenzymes?

Accepted Answer

They are irreversibly changed during catalysis.

Question 16

Which of the following best explains why substrate-level control is considered a crude means of enzyme regulation?

Accepted Answer

A large change in substrate concentration $$[S] is $$required to significantly affect enzyme activity.

Question 17

Which of the following is an example of irreversible covalent modification in enzyme regulation?

Accepted Answer

Activation of zymogens by proteolytic cleavage

Question 18

Which of the following statements about enzyme inhibition by prescription drugs is correct?

Accepted Answer

Many prescription drugs act as enzyme inhibitors, often by reversible or irreversible mechanisms.

Question 19

Which of the following is a correct statement about the effect of competitive inhibitors on enzyme kinetics?

Accepted Answer

They increase the apparent $$K_m$$ but do not affect $$V_{max}.$$

Question 20

Which of the following is a real-world example of enzyme regulation by covalent modification?

Accepted Answer

Blood clotting cascade activation by proteolytic cleavage of zymogens

Enzymes: Biological Catalysts – Principles, Mechanisms, and Regulation

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