Question 1

Which of these antibiotics acts by forming a covalent derivative of the enzyme glycoprotein peptidase?

Accepted Answer

A)  antimycin
B)  neomycin
C)  oligomycin
D)  penicillinE) None of the above
F) A) and D)

Question 2

In the enzyme catalyzed reaction sequence below,can the E-PO₄- intermediate be predicted and why?

Accepted Answer

A)  Yes,the mechanism is a double-displacement reaction.
B)  Yes,the reaction fits the Ping-Pong model.
C)  No,the reaction is random single displacement.
D)  No,the reaction is double displacement.E) B) and D)
F) All of the above

Question 3

A plot of 1/V versus 1/[S] for an enzyme-catalyzed reaction gave a line with an equation of y = 0.5x + 0.2.The same enzyme with an inhibitor present gave a line with an equation of y = 1.1x + 0.2.Which of these statements is correct regarding the inhibition?

Accepted Answer

A)  It is competitive.
B)  It is non-competitive.
C)  It is uncompetitive.
D)  It is irreversible.E) C) and D)
F) A) and B)

Question 4

Which of the following is correct regarding the Michaelis-Menten constant,Km,for this kinetic mechanism?
m is numerically equal to the substrate concentration required to achieve one half the maximum velocity. B) Its defined as Km = k1/(k-1 + k2) . C) Km is approximately equal to the dissociation constant for the enzyme-substrate complex to E + P. D) The numeric value of Km has the units of mole-1." class="answers-bank-image d-inline" rel="preload" >

Accepted Answer

A)  Km is numerically equal to the substrate concentration required to achieve one half the maximum velocity.
B)  Its defined as Km = k1/(k-1 + k2) .
C)  Km is approximately equal to the dissociation constant for the enzyme-substrate complex to E + P.
D)  The numeric value of Km has the units of mole-1.E) None of the above
F) B) and C)

Question 5

Which of the following is a feature of uncompetitive inhibition?

Accepted Answer

A)  I combines only with ES.
B)  I combines only with E.
C)  I combines with E and ES.
D)  I combines with EP.E) B) and C)
F) A) and B)

Question 6

What is the basis for the International Units of an enzyme?

Accepted Answer

A)  ratio of enzyme to other proteins
B)  micromoles of product formed per minute
C)  moles of substrate reacted
D)  micromoles of product produced at Vmax/2E) B) and D)
F) C) and D)

Question 7

What term describes an enzyme that is an ATP-dependent phosphotransferase?

Accepted Answer

A)  isomerase
B)  uricase
C)  protease
D)  kinaseE) B) and C)
F) All of the above

Question 8

Which reaction would NOT proceed via bimolecular elementary steps?

Accepted Answer

A)  C + D→ T + U
B)  a reaction with a rate constant in the units of s-1
C)  2A →D + E
D)  a reaction with a molecularity of 2E) B) and C)
F) A) and B)

Question 9

Which term defines the catalytically active complex of an apoenzyme and its prosthetic group?

Accepted Answer

A)  catalytic duo
B)  holoenzyme
C)  prosthetic enzyme
D)  dimeric enzymeE) B) and C)
F) None of the above

Question 10

For an enzyme-catalyzed reaction,the initial velocity was determined at 2 different concentrations of the substrate.Which of the following would be closest to the value of Vmₐₓ?

Accepted Answer

A)  0.32 mM/min
B)  0.67 mM/min
C)  1.5 mM/min
D)  3.19 mM/minE) B) and C)
F) C) and D)

Question 11

In the reaction mechanism below,which components are competitive for binding to free enzyme E?

Accepted Answer

A)  P and A
B)  A and B
C)  B and Q
D)  Q and AE) None of the above
F) A) and B)

Question 12

What is the definition of the free energy of activation,∆G‡?

Accepted Answer

A)  the average free energy of the product formed
B)  the rate of a chemical reaction in relationship to the concentration of reactant molecules
C)  the energy required to raise the average energy of one mole of reactant to the transition state energy
D)  the amount of energy released by a spontaneous reactionE) None of the above
F) C) and D) C

Question 13

Which of the following is NOT correct regarding enzyme pathways?

Accepted Answer

A)  The most effective way to control the pathway is to regulate every enzyme in the pathway.
B)  An enzyme pathway always proceeds in only one direction,never in reverse.
C)  A regulatory enzyme is regulated only by molecules within the given pathway.
D)  Metabolic pathways are necessary since enzymes usually catalyze only one specific reaction.E) C) and D)
F) All of the above

Question 14

Which of the following is NOT correct regarding non-competitive inhibition?

Accepted Answer

A)  Non-competitive inhibitors interact with the enzyme as well as the enzyme-substrate complex.
B)  Increasing the concentration of [S] can overcome the inhibition.
C)  The Vmax value does not remain the same as for a reaction that is not inhibited.
D)  The inhibitor can cause a conformational change in the enzyme.E) A) and B)
F) A) and C) B

Question 15

Against which type of antigen is a catalytic antibody (abzyme) generated?

Accepted Answer

A)  an analog of the transition-state intermediate in the reaction
B)  the substrate of the reaction
C)  an analog of the product of the reaction
D)  an analog of the transition-state intermediate in the reaction.E) B) and C)
F) A) and D) A

Question 16

If an enzyme has a Vmₐₓ of 15 mM/min,what is the velocity if the substrate is present at ¼ of the Km?

Accepted Answer

A)  12 mM/min
B)  6 mM/min
C)  3.75 mM/min
D)  3 mM/minE) A) and C)
F) A) and B)

Question 17

Which of the following is NOT a distinctive feature of enzymes?

Accepted Answer

A)  regulatory
B)  catalytic activity
C)  ability to change ∆G
D)  specificityE) None of the above
F) A) and D)

Question 18

Which of the following is NOT correct regarding the transition state of a reaction?

Accepted Answer

A)  The transition state is located at the height of a free energy diagram.
B)  The transition state,once reached,indicates that there is a high probability that the reaction will occur.
C)  The energy required to raise the average energy of one mole of reactant to the transition state is the free energy of activation.
D)  The transition state energy level is the sum of the energy levels of the reactants and products.E) B) and C)
F) A) and D)

Question 19

Which of the following is NOT correct for catalysts?

Accepted Answer

A)  They work by lowering the energy of activation.
B)  The average energy of the reaction is unchanged.
C)  They combine transiently with the reactants,promoting a reactive transition state condition.
D)  They are regenerated after each third reaction cycle.E) B) and C)
F) C) and D)

Question 20

Which of the following is NOT a characteristic of ribozymes?

Accepted Answer

A)  They emerge from the reaction changed.
B)  They are substrate specific.
C)  They enhance the reaction rate.
D)  They are RNA molecules.E) A) and B)
F) A) and C)

Exam 12: Enzymes Kinetics and Specificity

Which of these antibiotics acts by forming a covalent derivative of the enzyme glycoprotein peptidase?

Correct AnswerverifiedShow Answer

In the enzyme catalyzed reaction sequence below,can the E-PO₄- intermediate be predicted and why?

Correct AnswerverifiedShow Answer

A plot of 1/V versus 1/[S] for an enzyme-catalyzed reaction gave a line with an equation of y = 0.5x + 0.2.The same enzyme with an inhibitor present gave a line with an equation of y = 1.1x + 0.2.Which of these statements is correct regarding the inhibition?

Correct AnswerverifiedShow Answer

Which of the following is correct regarding the Michaelis-Menten constant,Km,for this kinetic mechanism?

Correct AnswerverifiedShow Answer

Which of the following is a feature of uncompetitive inhibition?

Correct AnswerverifiedShow Answer

What is the basis for the International Units of an enzyme?

Correct AnswerverifiedShow Answer

What term describes an enzyme that is an ATP-dependent phosphotransferase?

Correct AnswerverifiedShow Answer

Which reaction would NOT proceed via bimolecular elementary steps?

Correct AnswerverifiedShow Answer

Which term defines the catalytically active complex of an apoenzyme and its prosthetic group?

Correct AnswerverifiedShow Answer

For an enzyme-catalyzed reaction,the initial velocity was determined at 2 different concentrations of the substrate.Which of the following would be closest to the value of Vmₐₓ?

Correct AnswerverifiedShow Answer

In the reaction mechanism below,which components are competitive for binding to free enzyme E?

Correct AnswerverifiedShow Answer

What is the definition of the free energy of activation,∆G‡?

Correct AnswerverifiedC

Which of the following is NOT correct regarding enzyme pathways?

Correct AnswerverifiedShow Answer

Which of the following is NOT correct regarding non-competitive inhibition?

Correct AnswerverifiedB

Against which type of antigen is a catalytic antibody (abzyme) generated?

Correct AnswerverifiedA

If an enzyme has a Vmₐₓ of 15 mM/min,what is the velocity if the substrate is present at ¼ of the Km?

Correct AnswerverifiedShow Answer

Which of the following is NOT a distinctive feature of enzymes?

Correct AnswerverifiedShow Answer

Which of the following is NOT correct regarding the transition state of a reaction?

Correct AnswerverifiedShow Answer

Which of the following is NOT correct for catalysts?

Correct AnswerverifiedShow Answer

Which of the following is NOT a characteristic of ribozymes?

Correct AnswerverifiedShow Answer

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A plot of 1/V versus 1/[S] for an enzyme-catalyzed reaction gave a line with an equation of y = 0.5x + 0.2.The same enzyme with an inhibitor present gave a line with an equation of y = 1.1_x + 0.2.Which of these statements is correct regarding the inhibition?

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C

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B

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A

If an enzyme has a Vmₐₓ of 15 mM/min,what is the velocity if the substrate is present at ¼ of the K_m?

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