Question 1

Which statement best describes how a catalyst affects a chemical reaction?

Accepted Answer

A catalyst accelerates the approach to equilibrium by lowering the activation energy, but is not 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 of enzyme-substrate interaction, what happens when glucose binds to hexokinase?

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 transition state

Question 5

A patient is diagnosed with a deficiency in thiamine (vitamin B$_1$). Which coenzyme and reaction type would most likely be affected?

Accepted Answer

Thiamine pyrophosphate; activation and transfer of aldehydes

Question 6

Which metal ion is essential for the catalytic activity of alcohol dehydrogenase and helps bind NAD$^+$?

Accepted Answer

Zn

Question 7

A drug acts as a competitive inhibitor of an enzyme. Which of the following is true regarding its mechanism?

Accepted Answer

It competes with the substrate for binding at the enzyme's active site.

Question 8

Which type of reversible enzyme inhibition involves the inhibitor binding only to the enzyme-substrate (ES) complex?

Accepted Answer

Uncompetitive inhibition

Question 9

Diisopropyl fluorophosphate (DFP) causes paralysis by which mechanism?

Accepted Answer

Covalent modification of the active site serine in acetylcholinesterase

Question 10

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

Accepted Answer

Feedback inhibition at committed steps

Question 11

Allosteric enzymes typically exhibit which of the following properties?

Accepted Answer

They are multisubunit proteins that change conformation upon binding substrates or effectors.

Question 12

Which statement about covalent modification of enzymes is correct?

Accepted Answer

Phosphorylation by kinases can be reversed by dephosphorylation via phosphatases.

Question 13

Which of the following is an example of a nonprotein biocatalyst?

Accepted Answer

Ribozyme

Question 14

A researcher observes that an inhibitor binds to both the free enzyme and the ES complex at a site different from the substrate. What type of inhibition is this?

Accepted Answer

Mixed (noncompetitive) inhibition

Question 15

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 16

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

Accepted Answer

Increasing the activation energy of the substrate

Question 17

Which vitamin is required for the synthesis of the coenzyme tetrahydrofolate, and what is its primary function?

Accepted Answer

Folic acid; activation and transfer of single-carbon functional groups

Question 18

Which statement about substrate level control of enzyme activity is correct?

Accepted Answer

Large changes in substrate concentration are required to significantly affect enzyme activity.

Question 19

Which of the following best describes homoallostery in enzymes?

Accepted Answer

Cooperativity in substrate binding among multisubunit enzymes

Question 20

Which of the following statements about the 'RNA World' hypothesis is correct?

Accepted Answer

RNA molecules could both store genetic information and catalyze reactions before the evolution of DNA and proteins.

Chapter 8: Enzymes – Biological Catalysts (Biochemistry Study Notes)

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