BIO-CHEMISTRY FINAL EXAM 140 QUESTIONS AND DETAILED ANSWERS 2024-
2025 LATEST UPDATE ALREADY GRADED A+
One of the enzymes involved in glycolysis, aldolase, requires Zn2+ for catalysis. Under conditions of zinc
deficiency, when the enzyme may lack zinc, it would be referred to as the:
A) apoenzyme.
B) coenzyme.
C) holoenzyme.
D) prosthetic group.
E) substrate. - answer-A) apoenzyme.
Which one of the following is not among the six internationally accepted classes of enzymes?
A) Hydrolases
B) Ligases
C) Oxidoreductases
D) Polymerases
E) Transferases - answer-E) Transferases
Enzymes are potent catalysts because they:
A) are consumed in the reactions they catalyze.
B) are very specific and can prevent the conversion of products back to substrates.
C) drive reactions to completion while other catalysts drive reactions to equilibrium.
D) increase the equilibrium constants for the reactions they catalyze.
E) lower the activation energy for the reactions they catalyze. - answer-E) lower the activation energy
for the reactions they catalyze.
The role of an enzyme in an enzyme-catalyzed reaction is to:
A) bind a transition state intermediate, such that it cannot be converted back to substrate.
B) ensure that all of the substrate is converted to product.
C) ensure that the product is more stable than the substrate.
,D) increase the rate at which substrate is converted into product.
E) make the free-energy change for the reaction more favorable. - answer-D) increase the rate at which
substrate is converted into product.
Which one of the following statements is true of enzyme catalysts?
A) Their catalytic activity is independent of pH.
B) They are generally equally active on D and L isomers of a given substrate.
C) They can increase the equilibrium constant for a given reaction by a thousand fold or more.
D) They can increase the reaction rate for a given reaction by a thousand fold or more.
E) To be effective, they must be present at the same concentration as their substrate. - answer-D) They
can increase the reaction rate for a given reaction by a thousand fold or more.
Which one of the following statements is true of enzyme catalysts?
A) They bind to substrates, but are never covalently attached to substrate or product.
B) They increase the equilibrium constant for a reaction, thus favoring product formation.
C) They increase the stability of the product of a desired reaction by allowing ionizations,
resonance, and isomerizations not normally available to substrates.
D) They lower the activation energy for the conversion of substrate to product.
E) To be effective they must be present at the same concentration as their substrates. - answer-D) They
lower the activation energy for the conversion of substrate to product.
Which of the following statements is false?
A) A reaction may not occur at a detectable rate even though it has a favorable equilibrium.
B) After a reaction, the enzyme involved becomes available to catalyze the reaction again.
C) For S → P, a catalyst shifts the reaction equilibrium to the right.
D) Lowering the temperature of a reaction will lower the reaction rate.
E) Substrate binds to an enzyme's active site. - answer-C) For S → P, a catalyst shifts the reaction
equilibrium to the right.
Enzymes differ from other catalysts in that only enzymes:
,A) are not consumed in the reaction.
B) display specificity toward a single reactant.
C) fail to influence the equilibrium point of the reaction.
D) form an activated complex with the reactants.
E) lower the activation energy of the reaction catalyzed. - answer-B) display specificity toward a single
reactant.
Which of the following is true of the binding energy derived from enzyme-substrate interactions?
A) It cannot provide enough energy to explain the large rate accelerations brought about by enzymes.
B) It is sometimes used to hold two substrates in the optimal orientation for reaction.
C) It is the result of covalent bonds formed between enzyme and substrate.
D) Most of it is derived from covalent bonds between enzyme and substrate.
E) Most of it is used up simply binding the substrate to the enzyme. - answer-B) It is sometimes used to
hold two substrates in the optimal orientation for reaction.
The concept of "induced fit" refers to the fact that:
A) enzyme specificity is induced by enzyme-substrate binding.
B) enzyme-substrate binding induces an increase in the reaction entropy, thereby catalyzing the
reaction.
C) enzyme-substrate binding induces movement along the reaction coordinate to the transition state.
D) substrate binding may induce a conformational change in the enzyme, which then brings catalytic
groups into proper orientation.
E) when a substrate binds to an enzyme, the enzyme induces a loss of water (desolvation) from the
substrate. - answer-D) substrate binding may induce a conformational change in the enzyme, which then
brings catalytic groups into proper orientation.
The benefit of measuring the initial rate of a reaction V0 is that at the beginning of a reaction:
A) [ES] can be measured accurately.
B) changes in [S] are negligible, so [S] can be treated as a constant.
C) changes in Km are negligible, so Km can be treated as a constant.
, D) V0 = Vmax.
E) varying [S] has no effect on V0. - answer-B) changes in [S] are negligible, so [S] can be treated as a
constant.
Which of the following statements about a plot of V0 vs. [S] for an enzyme that follows Michaelis-
Menten kinetics is false?
A) As [S] increases, the initial velocity of reaction V0 also increases.
B) At very high [S], the velocity curve becomes a horizontal line that intersects the y-axis at Km.
C) Km is the [S] at which V0 = 1/2 Vmax.
D) The shape of the curve is a hyperbola.
E) The y-axis is a rate term with units of μm/min. - answer-B) At very high [S], the velocity curve
becomes a horizontal line that intersects the y-axis at Km.
The steady state assumption, as applied to enzyme kinetics, implies:
A) Km = Ks.
B) the enzyme is regulated.
C) the ES complex is formed and broken down at equivalent rates.
D) the Km is equivalent to the cellular substrate concentration.
E) the maximum velocity occurs when the enzyme is saturated. - answer-C) the ES complex is formed
and broken down at equivalent rates.
An enzyme-catalyzed reaction was carried out with the substrate concentration initially a thousand
times greater than the Km for that substrate. After 9 minutes, 1% of the substrate had been converted
to product, and the amount of product formed in the reaction mixture was 12 μmol. If, in a separate
experiment, one-third as much enzyme and twice as much substrate had been combined, how long
would it take for the same amount (12 μmol) of product to be formed?
A) 1.5 min
B) 13.5 min
C) 27 min
D) 3 min
2025 LATEST UPDATE ALREADY GRADED A+
One of the enzymes involved in glycolysis, aldolase, requires Zn2+ for catalysis. Under conditions of zinc
deficiency, when the enzyme may lack zinc, it would be referred to as the:
A) apoenzyme.
B) coenzyme.
C) holoenzyme.
D) prosthetic group.
E) substrate. - answer-A) apoenzyme.
Which one of the following is not among the six internationally accepted classes of enzymes?
A) Hydrolases
B) Ligases
C) Oxidoreductases
D) Polymerases
E) Transferases - answer-E) Transferases
Enzymes are potent catalysts because they:
A) are consumed in the reactions they catalyze.
B) are very specific and can prevent the conversion of products back to substrates.
C) drive reactions to completion while other catalysts drive reactions to equilibrium.
D) increase the equilibrium constants for the reactions they catalyze.
E) lower the activation energy for the reactions they catalyze. - answer-E) lower the activation energy
for the reactions they catalyze.
The role of an enzyme in an enzyme-catalyzed reaction is to:
A) bind a transition state intermediate, such that it cannot be converted back to substrate.
B) ensure that all of the substrate is converted to product.
C) ensure that the product is more stable than the substrate.
,D) increase the rate at which substrate is converted into product.
E) make the free-energy change for the reaction more favorable. - answer-D) increase the rate at which
substrate is converted into product.
Which one of the following statements is true of enzyme catalysts?
A) Their catalytic activity is independent of pH.
B) They are generally equally active on D and L isomers of a given substrate.
C) They can increase the equilibrium constant for a given reaction by a thousand fold or more.
D) They can increase the reaction rate for a given reaction by a thousand fold or more.
E) To be effective, they must be present at the same concentration as their substrate. - answer-D) They
can increase the reaction rate for a given reaction by a thousand fold or more.
Which one of the following statements is true of enzyme catalysts?
A) They bind to substrates, but are never covalently attached to substrate or product.
B) They increase the equilibrium constant for a reaction, thus favoring product formation.
C) They increase the stability of the product of a desired reaction by allowing ionizations,
resonance, and isomerizations not normally available to substrates.
D) They lower the activation energy for the conversion of substrate to product.
E) To be effective they must be present at the same concentration as their substrates. - answer-D) They
lower the activation energy for the conversion of substrate to product.
Which of the following statements is false?
A) A reaction may not occur at a detectable rate even though it has a favorable equilibrium.
B) After a reaction, the enzyme involved becomes available to catalyze the reaction again.
C) For S → P, a catalyst shifts the reaction equilibrium to the right.
D) Lowering the temperature of a reaction will lower the reaction rate.
E) Substrate binds to an enzyme's active site. - answer-C) For S → P, a catalyst shifts the reaction
equilibrium to the right.
Enzymes differ from other catalysts in that only enzymes:
,A) are not consumed in the reaction.
B) display specificity toward a single reactant.
C) fail to influence the equilibrium point of the reaction.
D) form an activated complex with the reactants.
E) lower the activation energy of the reaction catalyzed. - answer-B) display specificity toward a single
reactant.
Which of the following is true of the binding energy derived from enzyme-substrate interactions?
A) It cannot provide enough energy to explain the large rate accelerations brought about by enzymes.
B) It is sometimes used to hold two substrates in the optimal orientation for reaction.
C) It is the result of covalent bonds formed between enzyme and substrate.
D) Most of it is derived from covalent bonds between enzyme and substrate.
E) Most of it is used up simply binding the substrate to the enzyme. - answer-B) It is sometimes used to
hold two substrates in the optimal orientation for reaction.
The concept of "induced fit" refers to the fact that:
A) enzyme specificity is induced by enzyme-substrate binding.
B) enzyme-substrate binding induces an increase in the reaction entropy, thereby catalyzing the
reaction.
C) enzyme-substrate binding induces movement along the reaction coordinate to the transition state.
D) substrate binding may induce a conformational change in the enzyme, which then brings catalytic
groups into proper orientation.
E) when a substrate binds to an enzyme, the enzyme induces a loss of water (desolvation) from the
substrate. - answer-D) substrate binding may induce a conformational change in the enzyme, which then
brings catalytic groups into proper orientation.
The benefit of measuring the initial rate of a reaction V0 is that at the beginning of a reaction:
A) [ES] can be measured accurately.
B) changes in [S] are negligible, so [S] can be treated as a constant.
C) changes in Km are negligible, so Km can be treated as a constant.
, D) V0 = Vmax.
E) varying [S] has no effect on V0. - answer-B) changes in [S] are negligible, so [S] can be treated as a
constant.
Which of the following statements about a plot of V0 vs. [S] for an enzyme that follows Michaelis-
Menten kinetics is false?
A) As [S] increases, the initial velocity of reaction V0 also increases.
B) At very high [S], the velocity curve becomes a horizontal line that intersects the y-axis at Km.
C) Km is the [S] at which V0 = 1/2 Vmax.
D) The shape of the curve is a hyperbola.
E) The y-axis is a rate term with units of μm/min. - answer-B) At very high [S], the velocity curve
becomes a horizontal line that intersects the y-axis at Km.
The steady state assumption, as applied to enzyme kinetics, implies:
A) Km = Ks.
B) the enzyme is regulated.
C) the ES complex is formed and broken down at equivalent rates.
D) the Km is equivalent to the cellular substrate concentration.
E) the maximum velocity occurs when the enzyme is saturated. - answer-C) the ES complex is formed
and broken down at equivalent rates.
An enzyme-catalyzed reaction was carried out with the substrate concentration initially a thousand
times greater than the Km for that substrate. After 9 minutes, 1% of the substrate had been converted
to product, and the amount of product formed in the reaction mixture was 12 μmol. If, in a separate
experiment, one-third as much enzyme and twice as much substrate had been combined, how long
would it take for the same amount (12 μmol) of product to be formed?
A) 1.5 min
B) 13.5 min
C) 27 min
D) 3 min
