Question 1

Which of the following is true about enzymes?

Accepted Answer

A)   enzymes show very little specificity for their substrates
B)   enzymes catalyze reactions in only one direction
C)   enzyme activities can often be regulated
D)   enzymes reaction rates are generally slower than other chemical catalysts
E)   enzymes operate under a wide range of temperatures and pHF) B) and E)
G) A) and E)

Question 2

In a bisubstrate reaction, reactant A binds and is then converted to product C. Next, reactant B binds and is then converted to product D. An experiment showed that B cannot bind without C being released first. What mechanism is indicated by this data?

Accepted Answer

A)   ordered mechanism
B)   random mechanism
C)   ping pong mechanism
D)   cooperative mechanism
E)   none of the aboveF) A) and D)
G) D) and E)

Question 3

For a reaction A + B  →\rarr→  C, if [B] is much larger than [A] so that [B] essentially remains constant over the course of the reaction, the kinetics will be _____.

Accepted Answer

A)   zero-order
B)   hyperbolic
C)   first-order
D)   sigmoidal
E)   pseudo first-order F) A) and B)
G) C) and D)

Question 4

Which of the following properly expresses the Michaelis-Menten equation?

Accepted Answer

A)   vo = Vmax [S] / (KM + [S]) 
B)   vo = Vmax KM / (KM + [S]) 
C)   kcat = Vmax / [E]T
D)   Vmax = vo [S] / (KM + [S]) 
E)   Vmax = vo KM / (KM + [S]) F) C) and E)
G) B) and D)

Question 5

How are the kinetics of an enzyme-catalyzed reaction affected by a purely noncompetitive inhibitor?

Accepted Answer

A)   Vmax decreased, KM increased
B)   Vmax decreased, KM decreased
C)   Vmax decreased, KM unchanged
D)   Vmax unchanged, KM increased
E)   Vmax unchanged, KM decreasedF) All of the above
G) D) and E)

Question 6

What percentage of Vmax is obtained when the substrate is present at ¼ of the KM?
`

Accepted Answer

A)   5%
B)   20%
C)   25%
D)   80%
E)   100%F) B) and C)
G) C) and E)

Question 7

Acyclovir is an analog of ___ that lacks interferes with ___.

Accepted Answer

guanosine,...

Question 8

In a bisubstrate reaction, reactant A binds, followed by reactant B which then get converted to products C and D. An experiment showed that B cannot bind without A having bound first. What mechanism is indicated by this data?

Accepted Answer

A)   ordered mechanism
B)   random mechanism
C)   ping pong mechanism
D)   cooperative mechanism
E)   none of the aboveF) C) and E)
G) A) and E)

Question 9

Which of the following must be true for an enzymatic reaction obeying the Michaelis-Menten equation to reach 3/4 of its maximum velocity?

Accepted Answer

A)   [S] must be ¾KM
B)   [S] must be 1.5KM
C)   [S] must be 2KM
D)   [S] must be 3KM
E)   [S] must be 4KMF) A) and D)
G) None of the above

Question 10

When is KM considered to be the same as the dissociation constant for the ES complex i.e., KM   ≈\approx≈  [E] [S] / [ES].

Accepted Answer

A)   ES  →\rarr→  E + P is fast compared to ES  →\rarr→  E + S
B)   the turnover number is very large
C)   kcat/KM is near the diffusion-controlled limit
D)   k2 -1
E)   KM can never be the same as the dissociation constant F) A) and B)
G) A) and C)

Question 11

How are the kinetics of an enzyme-catalyzed reaction affected by a mixed inhibitor?

Accepted Answer

A)   Vmax decreased, KM increased or decreased
B)   Vmax decreased, KM decreased
C)   Vmax decreased, KM increased
D)   Vmax unchanged, KM increased
E)   Vmax unchanged, KM increased or decreasedF) C) and D)
G) A) and B) A

Question 12

Which of the following types of enzyme-catalyzed reactions follows non-Michaelis-Menten kinetics?

Accepted Answer

A)   bisubstrate reactions with a random mechanism
B)   bisubstrate reactions with a ping pong mechanism
C)   bisubstrate reactions with an ordered mechanism
D)   allosteric enzyme reactions
E)   all of the aboveF) B) and E)
G) B) and D)

Question 13

How are the kinetics of an enzyme-catalyzed reaction affected by a competitive inhibitor?

Accepted Answer

A)   Vmax decreased, KM increased
B)   Vmax decreased, KM decreased
C)   Vmax decreased, KM unchanged
D)   Vmax unchanged, KM increased
E)   Vmax unchanged, KM decreasedF) A) and B)
G) A) and E)

Question 14

What type of inhibition explains why even at very high substrate concentrations, enzyme activity will decrease as time increases?

Accepted Answer

A)   allosteric inhibition
B)   product inhibition
C)   transition state analogs
D)   irreversible inhibition
E)   uncompetitive inhibitionF) C) and D)
G) None of the above

Question 15

Find the initial velocity for an enzymatic reaction when Vmax = 6.5 × 10-5 mol•sec-1, [S] = 3.0 × 10-3 M, KM = 4.5 × 10-3 M, and the enzyme concentration at time zero is 1.5 × 10-2 μ\muμ M.

Accepted Answer

A)   3.9 × 10-5 mol•sec-1
B)   2.6 × 10-5 mol•sec-1
C)   1.4 × 10-2 mol•sec-1
D)   8.7 × 10-3 mol•sec-1
E)   Not enough information is given to make this calculation. F) B) and D)
G) A) and D)

Question 16

Which of the following is true regarding transition state analogs?

Accepted Answer

A)   they are competitive inhibitors
B)   they bind to an active site with much higher affinity than most inhibitors
C)   they are much more stable than the transition state
D)   their affinity for an enzyme is often much greater that the substrate
E)   all of the aboveF) B) and C)
G) C) and E) E

Question 17

If a Lineweaver-Burk plot was made for an enzyme-catalyzed reaction, both with and without a competitive inhibitor present, what difference would be seen?

Accepted Answer

A)   the y-intercept would be lower for the inhibited reaction
B)   the y-intercept would be higher for the inhibited reaction
C)   the slope would be less for the inhibited reaction
D)   the slope would be greater for the inhibited reaction
E)   none of the aboveF) C) and E)
G) None of the above

Question 18

If a Lineweaver-Burk plot was made for an enzyme-catalyzed reaction, both with and without a noncompetitive inhibitor present, what difference would be seen?

Accepted Answer

A)   the y-intercept would be higher with slope unchanged for the inhibited reaction
B)   the y-intercept would be lower with larger slope for the inhibited reaction
C)   the y-intercept would be lower with smaller slope for the inhibited reaction
D)   the y-intercept would be higher with larger slope for the inhibited reaction
E)   the y-intercept would be higher with smaller slope for the inhibited reactionF) B) and E)
G) A) and B) D

Question 19

How is an enzyme-catalyzed reaction affected by the addition of more enzyme?

Accepted Answer

A)   velocity is not effected
B)   velocity will increase only if more substrate is also added
C)   velocity will increase
D)   velocity will decrease
E)   none of the aboveF) None of the above
G) All of the above

Question 20

Find kcat for a reaction in which Vmax is 4 × 10-4 mol•min-1 and the reaction mixture contains one microgram of enzyme (the molecular weight of the enzyme is 200,000

Accepted Answer

A)   2 × 10-11 min-1
B)   8 × 107 min-1
C)   8 × 109 min-1
D)   2 × 10-14 min-1
E)   4 × 108 min-1F) B) and D)
G) B) and C)

Exam 7: Enzyme Kinetics and Inhibition

Which of the following is true about enzymes?

Correct AnswerverifiedShow Answer

In a bisubstrate reaction, reactant A binds and is then converted to product C. Next, reactant B binds and is then converted to product D. An experiment showed that B cannot bind without C being released first. What mechanism is indicated by this data?

Correct AnswerverifiedShow Answer

For a reaction A + B →\rarr→ C, if [B] is much larger than [A] so that [B] essentially remains constant over the course of the reaction, the kinetics will be _____.

Correct AnswerverifiedShow Answer

Which of the following properly expresses the Michaelis-Menten equation?

Correct AnswerverifiedShow Answer

How are the kinetics of an enzyme-catalyzed reaction affected by a purely noncompetitive inhibitor?

Correct AnswerverifiedShow Answer

What percentage of Vmax is obtained when the substrate is present at ¼ of the KM? `

Correct AnswerverifiedShow Answer

Acyclovir is an analog of ___ that lacks interferes with ___.

Correct Answerverifiedguanosine,...View AnswerShow Answer

In a bisubstrate reaction, reactant A binds, followed by reactant B which then get converted to products C and D. An experiment showed that B cannot bind without A having bound first. What mechanism is indicated by this data?

Correct AnswerverifiedShow Answer

Which of the following must be true for an enzymatic reaction obeying the Michaelis-Menten equation to reach 3/4 of its maximum velocity?

Correct AnswerverifiedShow Answer

When is KM considered to be the same as the dissociation constant for the ES complex i.e., KM ≈\approx≈ [E] [S] / [ES].

Correct AnswerverifiedShow Answer

How are the kinetics of an enzyme-catalyzed reaction affected by a mixed inhibitor?

Correct AnswerverifiedA

Which of the following types of enzyme-catalyzed reactions follows non-Michaelis-Menten kinetics?

Correct AnswerverifiedShow Answer

How are the kinetics of an enzyme-catalyzed reaction affected by a competitive inhibitor?

Correct AnswerverifiedShow Answer

What type of inhibition explains why even at very high substrate concentrations, enzyme activity will decrease as time increases?

Correct AnswerverifiedShow Answer

Find the initial velocity for an enzymatic reaction when Vmax = 6.5 × 10-5 mol•sec-1, [S] = 3.0 × 10-3 M, KM = 4.5 × 10-3 M, and the enzyme concentration at time zero is 1.5 × 10-2 μ\muμ M.

Correct AnswerverifiedShow Answer

Which of the following is true regarding transition state analogs?

Correct AnswerverifiedE

If a Lineweaver-Burk plot was made for an enzyme-catalyzed reaction, both with and without a competitive inhibitor present, what difference would be seen?

Correct AnswerverifiedShow Answer

If a Lineweaver-Burk plot was made for an enzyme-catalyzed reaction, both with and without a noncompetitive inhibitor present, what difference would be seen?

Correct AnswerverifiedD

How is an enzyme-catalyzed reaction affected by the addition of more enzyme?

Correct AnswerverifiedShow Answer

Find kcat for a reaction in which Vmax is 4 × 10-4 mol•min-1 and the reaction mixture contains one microgram of enzyme (the molecular weight of the enzyme is 200,000

Correct AnswerverifiedShow Answer

Correct Answer
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Correct Answer
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For a reaction A + B $\rarr$ C, if [B] is much larger than [A] so that [B] essentially remains constant over the course of the reaction, the kinetics will be _____.

Correct Answer
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Correct Answer
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What percentage of V_max is obtained when the substrate is present at ¼ of the K_M? `

Correct Answer
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Acyclovir is an analog of _ that lacks interferes with _.

Correct Answer
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guanosine,...
View Answer

Correct Answer
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Correct Answer
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When is K_M considered to be the same as the dissociation constant for the ES complex i.e., K_M $\approx$ [E] [S] / [ES].

Correct Answer
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A

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Find the initial velocity for an enzymatic reaction when V_max = 6.5 × 10^-5 mol•sec^-1, [S] = 3.0 × 10^-3 M, K_M = 4.5 × 10^-3 M, and the enzyme concentration at time zero is 1.5 × 10^-2 $\mu$ M.

Correct Answer
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Correct Answer
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E

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D

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Correct Answer
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