Question 1

Which of the following statements best describes the induced fit model of enzyme-substrate binding?

Accepted Answer

The enzyme changes conformation after the substrate binds, optimizing interactions for catalysis.

Question 2

Hexokinase catalyzes the phosphorylation of glucose. When glucose binds, the enzyme undergoes a conformational change that excludes water from the active site. What is the primary reason for this exclusion?

Accepted Answer

To prevent hydrolysis of ATP by water.

Question 3

Which of the following is a key advantage of enzymes over inorganic catalysts such as metal ions?

Accepted Answer

Enzymes have high specificity for their substrates and can regulate their activity.

Question 4

Enolase, an enzyme in glycolysis, requires $$\mathrm{Mg$$^{2+}$$}$$ for activity. What type of catalytic mechanism does enolase use?

Accepted Answer

Metal ion catalysis

Question 5

Which of the following statements about cofactors and coenzymes is most accurate?

Accepted Answer

Coenzymes are enzyme cofactors that require organic components, often derived from vitamins.

Question 6

Which of the following best explains how enzymes increase the rate of chemical reactions?

Accepted Answer

By lowering the activation energy $$\Delta G$$^{\ddagger}$$ required to reach the transition state.

Question 7

A mutation in the active site of an enzyme stabilizes the enzyme-substrate (ES) complex but does not affect the transition state. What is the likely effect on the rate of product formation?

Accepted Answer

The rate of product formation decreases because the energy barrier between ES and the transition state increases.

Question 8

Which of the following is a property of transition state analogs used as enzyme inhibitors?

Accepted Answer

They mimic the structure of the transition state and bind tightly to the active site.

Question 9

Which of the following amino acids is most likely to participate in general acid-base catalysis in an enzyme active site at physiological pH?

Accepted Answer

Histidine

Question 10

Which of the following best describes the role of NAD$$^+/$$NADH in enzymatic reactions?

Accepted Answer

NAD$$^+$$ acts as a mobile two-electron carrier, transferring electrons between enzymes.

Question 11

Which of the following mechanisms involves a nucleophilic group on the enzyme attacking an electrophilic center on the substrate to form a covalent intermediate?

Accepted Answer

Covalent catalysis

Question 12

Which of the following is NOT a common way enzymes increase reaction rates?

Accepted Answer

Changing the equilibrium constant $$K_{eq} of $$the reaction

Question 13

Which of the following statements about enzyme nomenclature is correct?

Accepted Answer

Most enzyme names end in '-ase' and include the substrate name.

Question 14

Which of the following is an example of a metabolic transformation reaction catalyzed by enzymes?

Accepted Answer

Phosphorylation of a protein by a kinase

Question 15

Which of the following best describes the conformational selection mechanism of enzyme-substrate binding?

Accepted Answer

The enzyme exists in multiple conformations before substrate binding, and the substrate binds to the most favorable one.

Question 16

Which metal ion is required by carbonic anhydrase to support nucleophilic attack on $$\mathrm{CO_2$}$$?

Accepted Answer

$$\mathrm{Zn$$^{2+}$$}$$

Question 17

Which of the following statements about the stabilization of the transition state by enzymes is correct?

Accepted Answer

Enzymes bind the transition state more tightly than the substrate, lowering the activation energy.

Question 18

Which of the following is a property of the active site microenvironment that promotes catalysis?

Accepted Answer

It provides optimal orientation of the substrate and excludes excess solvent.

Question 19

Which of the following is an example of reversible covalent modification in enzyme-mediated reactions?

Accepted Answer

Phosphorylation and dephosphorylation of a protein

Chapter 7: Enzyme Mechanisms – Study Notes for Biochemistry I

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