Chapter 6 Self-test questions

. Which of the following statements about the active site of an enzyme is correct?

The active site of an enzyme binds the substrate of the reaction it catalyses more tightly than it does the transition state intermediate.

The active site of an enzyme binds the substrate of the reaction it catalyses less tightly than it does the transition state intermediate.

The active site of an enzyme binds the product of the reaction it catalyses more tightly than it does the transition state intermediate.

The active site of an enzyme is complementary to the substrate of the reaction it catalyses.

. Which of the following statements about the nature of enzyme catalysis is correct?

An enzyme can change the equilibrium position of the reaction it catalyses by lowering the energy of activation of that reaction.

An enzyme can lower the energy of activation of the reaction it catalyses by increasing the molecular collisions between the molecules.

An enzyme lowers the free energy difference between substrate(s) and product(s) but it cannot change the equilibrium position of the reaction it catalyses.

An enzyme cannot change the equilibrium position of the reaction it catalyses but it lowers the energy of activation of that reaction.

. Which of the following statements about Michaelis-Menten kinetics is correct?

K_m, the Michaelis constant, is defined as the concentration of substrate required for the reaction to reach maximum velocity.

K_m, the Michaelis constant, is defined as the dissociation constant of the enzyme-substrate complex.

K_m, the Michaelis constant, is expressed in terms of the reaction velocity.

K_m, the Michaelis constant, is a measure of the affinity the enzyme has for its substrate.

. Which of the following statements about the competitive inhibition of an enzyme-catalyzed reaction is correct?

A competitive inhibitor and substrate can bind simultaneously to the enzyme.

The V_max and K_m (Michaelis constant) for a reaction are unchanged in the presence of a competitive inhibitor.

The V_max for a reaction remains unchanged in the presence of a competitive inhibitor.

The K_m for a reaction remains unchanged in the presence of a competitive inhibitor.

. Which of the following statements about the mechanism of allosteric control of enzyme activity is correct?

Allosteric enzymes are typically single-subunit enzymes.

Allosteric enzymes show greater sensitivity to changes in substrate concentration compared to classical type enzymes with hyperbolic kinetics.

Allosteric enzymes show Michaelis-Menten kinetics.

Allosteric enzymes show reduced sensitivity to changes in substrate concentration compared to classical type enzymes with hyperbolic kinetics.

. Which of the following statements about the mechanism of the catalytic triad of chymotrypsin is correct?

A proton moves from the serine to the histidine to the aspartate side chain in the catalytic triad of chymotrypsin.

A proton moves from the aspartate to the serine to the histidine side chain in the catalytic triad of chymotrypsin.

A proton moves from the serine to the histidine side chain in the catalytic triad of chymotrypsin.

A proton moves from the aspartate to the histidine side chain in the catalytic triad of chymotrypsin.

. Which of the following statements about the nature of enzyme catalysis is correct?

The rate of formation of the transition state intermediate determines the overall free energy change of the reaction.

The active site of an enzyme is perfectly complementary to the substrate in its ground state.

The rate of formation of the transition state intermediate determines the overall reaction rate.

Natural substrates bind to enzymes more tightly than transition state analogues.

. Which of the following statements about allosteric enzymes is correct?

Allosteric enzymes display Michaelis-Menten kinetics.

Allosteric enzymes are usually single subunit enzymes.

Allosteric enzymes control metabolism.

Allosteric enzymes display hyperbolic kinetics in response to changes in substrate concentration.

. Which of the following statements about competitive inhibition of an enzyme-catalyzed reaction is correct?

The addition of large amounts of substrate to a reaction cannot overcome the effect of a competitive inhibitor.

A competitive inhibitor can bind to the enzyme-substrate complex.

Competitive inhibition can be overcome by the addition of large amounts of substrate to a reaction.

The V_max of a reaction decreases in the presence of a competitive inhibitor.

. Which of the following statements about Lineweaver-Burk plots are correct? Please select all that apply.

All enzyme-catalysed reactions give a linear Lineweaver-Burk plot.

A Lineweaver-Burk plot provides estimates of V_max and K_m for allosteric enzymes.

A Lineweaver-Burk plot for a classical enzyme is a straight line.

A Lineweaver-Burk plot for a classical enzyme can provide estimates of V_max and K_m by linear extrapolation.

. Which of the following statements about Michaelis-Menten kinetics are correct? Please select all that apply.

A high Michaelis constant (K_m) indicates a high affinity of an enzyme for its substrate.

A low Michaelis constant (K_m) indicates a high affinity of an enzyme for its substrate.

The Michaelis constant (K_m) of an enzyme increases when the enzyme concentration is increased.

The Michaelis constant (K_m) of an enzyme is unchanged when the enzyme concentration is increased.

. Which of the following statements about the reactions at the active centre of chymotrypsin are correct? Please select all that apply.

The aspartate residue in the active site of chymotrypsin donates a proton to histidine.

The aspartate residue in the active site of chymotrypsin holds the histidine in the correct orientation.

A proton moves from the aspartate to the serine to the histidine side chain in the catalytic triad of chymotrypsin.

The histidine residue in the active site of chymotrypsin accepts a proton to from water.

. Which of the following statements about the mechanism of the catalytic triad of chymotrypsin are correct? Please select all that apply.

A water molecule becomes unprotonated and protonated promoting general acid-base catalysis.

The serine side chain becomes protonated and unprotonated promoting general acid-base catalysis.

The histidine side chain becomes protonated and unprotonated promoting general acid-base catalysis.

The aspartate side chain holds the histidine in the correct orientation promoting general acid-base catalysis.

. Which of the following statements about Michaelis-Menten kinetics are correct? Please select all that apply.

Michaelis-Menten kinetics assume covalent binding occurs between enzyme and substrate.

Michaelis-Menten kinetics assume the enzyme and substrate first bind to form an enzyme-substrate complex.

Michaelis-Menten kinetics describe single substrate enzymes.

Michaelis-Menten kinetics apply only to reaction rates before the product is formed.

Chapter 6 Self-test questions

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