Question 1

Which of the following statements best describes the role of a catalyst in a chemical reaction?

Accepted Answer

A catalyst accelerates the approach to equilibrium without being changed in the overall process.

Question 2

Which major class of enzyme catalyzes the transfer of a phosphate group from ATP to glucose?

Accepted Answer

Transferase

Question 3

According to the induced fit model, what happens when a substrate binds to an enzyme?

Accepted Answer

The enzyme undergoes a conformational change to better accommodate the substrate.

Question 4

Which of the following mechanisms does NOT contribute to enzymatic rate acceleration?

Accepted Answer

Increasing the activation energy of the reaction

Question 5

Which equation best represents the reaction coordinate for a simple enzyme-catalyzed reaction?

Accepted Answer

$$E + S \xrightleftharpoons[k_{-1}]{k_1$} ES \xrightleftharpoons[k_{-2}]{k_2$} EP \xrightleftharpoons[k_{-3}]{k_3$} E + P$$

Question 6

Which statement about coenzymes and cofactors is correct?

Accepted Answer

Enzymes often require coenzymes or cofactors for efficient catalytic activity.

Question 7

Which metal ion is essential for the catalytic activity of alcohol dehydrogenase?

Accepted Answer

Zn

Question 8

Which type of enzyme inhibition involves the inhibitor binding noncovalently to the enzyme's active site, competing with the substrate?

Accepted Answer

Competitive inhibition

Question 9

In uncompetitive inhibition, the inhibitor binds:

Accepted Answer

Tightly to the enzyme-substrate (ES) complex

Question 10

Which of the following is an example of irreversible enzyme inhibition?

Accepted Answer

Diisopropyl fluorophosphate (DFP) covalently binding to acetylcholinesterase

Question 11

Which regulatory mechanism is most efficient for maintaining homeostasis in metabolic pathways?

Accepted Answer

Feedback inhibition at committed steps

Question 12

Allosteric enzymes are typically characterized by:

Accepted Answer

Multisubunit structure and conformational changes upon substrate or effector binding

Question 13

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

Accepted Answer

Phosphorylation by protein kinases and dephosphorylation by phosphatases

Question 14

Which statement about ribozymes is correct?

Accepted Answer

Ribozymes are ribonucleic acids that catalyze chemical reactions.

Question 15

Which vitamin is a precursor for the coenzyme thiamine pyrophosphate, involved in activation and transfer of aldehydes?

Accepted Answer

Thiamine (vitamin B1)

Question 16

Which of the following best describes the effect of phosphorylation on enzyme activity?

Accepted Answer

Phosphorylation can serve as a functional on or off switch for enzyme activity.

Question 17

Which equation represents the total enzyme concentration in the presence of a competitive inhibitor?

Accepted Answer

$$[E]_t = [E] + [ES] + [EI]$$

Question 18

Which of the following is NOT a mechanism by which enzymes achieve rate acceleration?

Accepted Answer

Increasing the activation energy of the transition state

Question 19

In the context of enzyme regulation, what is the primary function of feedback inhibition?

Accepted Answer

To maintain homeostasis by inhibiting an early step in a metabolic pathway when the end product accumulates

Question 20

Which of the following statements about allosteric regulation is true?

Accepted Answer

Allosteric enzymes can be regulated by nonsubstrate effector molecules (heteroallostery).

Chapter 8: Enzymes – Biological Catalysts

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