Question 1

Enzyme cofactors

Accepted Answer

A)   can be only inorganic ions or compounds.
B)   combine with the protein moiety of the enzyme to form an apoenzyme.
C)   are not know to combine simultaneously with both enzyme and substrate.
D)   can act only by helping to maintain the native conformation of the enzyme protein.
E)   may participate in the catalytic mechanism of an enzyme, providing a reactive group not found in the side chains of the common amino acids.

Question 2

Which of the following statements relative to the maximum velocity (Vmax)  of an enzyme catalyzed reaction (assayed under conditions of excess substrate)  is correct?

Accepted Answer

A)   Vmax is equal to twice the Km.
B)   Vmax is directly proportional to the concentration of the substrate.
C)   Vmax is reached when the concentration of the enzyme-substrate complex is equal to the original concentration of the enzyme.
D)   Vmax is reached if an enzyme concentration is used that is at least ten times higher than the Km.
E)   Vmax is independent of the enzyme concentration.

Question 3

When enzyme rate, the constraint on the ratio of k cat/Km must be kept in mind. Which values of the two constants, respectively, will give the greatest enzyme rate at a given substrate concentration?

Accepted Answer

A)   1 s -1 / 10-6 M
B)   102 s -1 / 10-4 M
C)   103 s -1 / 10-3 M
D)   104 s -1 / 10-2 M
E)   105 s -1 / 10-1 M

Question 4

Stereospecificity may be explained by

Accepted Answer

A)   the catalytic constant.
B)   reversibility of formation of the enzyme-substrate complex.
C)   three point attachment.
D)   competitive inhibitors.
E)   saturation.

Question 5

When the substrate concentration is equal to Km for a given enzyme and substrate you would expect which of the following?

Accepted Answer

A)   Vo = Vmax
B)   Vo = Vmax/2
C)   Vo = Vmax/3
D)   Vo = Vmax/4
E)   Vo = Vmax/10

Question 6

What is one good reason why initial velocities are employed in enzyme assays?

Accepted Answer

A)   Substrate inhibition is minimized.
B)   Substrate activation is minimized.
C)   Errors in technique are minimized.
D)   Product inhibition is minimized.
E)   The sensitivity of the assay is increased.

Question 7

Hydrolysis of high energy phosphate bonds associated with enzymatic linking of two molecules is catalyzed by what group of enzymes?

Accepted Answer

A)   Oxidoreductases
B)   Hydrolases
C)   Lyases
D)   Isomerases
E)   Ligases

Question 8

In the case of non-competitive inhibition, the inhibitor may bind to which of the following?

Accepted Answer

A)   only free enzyme
B)   only enzyme-substrate complex
C)   both free enzyme and enzyme?substrate complex
D)   only to substrate
E)   only to the substrate binding site of the enzyme

Question 9

Standard free energy of a reaction can be used for all of the following EXCEPT

Accepted Answer

A)   predict the direction in which a reaction will proceed under standard conditions of temperature, concentrations and pH.
B)   predict free energy changes for reactions given the concentrations of reactants and products that are unequal to 1 M.
C)   predict the rate of a chemical reaction.
D)   predict the standard free energy change of the reaction at pH 7.
E)   predict the equilibrium constant for a reaction.

Question 10

In the case of an enzyme displaying a sigmoid relationship between velocity and substrate concentration, it can be concluded that

Accepted Answer

A)   the binding of one substrate molecule hinders the binding of others.
B)   the enzyme contains only one binding site for substrate.
C)   substrate binds more easily at low concentrations than at high concentrations.
D)   the enzyme must contain at least four subunits.
E)   the enzyme displays cooperativity in terms of substrate binding.

Question 11

A measurement of cooperativity is the

Accepted Answer

A)   energy of activation.
B)   maximum velocity.
C)   inhibition constant.
D)   Hill coefficient.
E)   Arrhenius coefficient.

Question 12

The intercept on the vertical axis (Y-axis)  on a Lineweaver-Burk plot is equal to

Accepted Answer

A)   1/Km.
B)   1/Vmax.
C)   -1/Km.
D)   -1/Vmax.
E)   Vmax.

Question 13

The kinetics of a typical Michaelis-Menten enzyme shows what order dependence of substrate concentration at very high substrate concentrations?

Accepted Answer

A)   zero
B)   first
C)   second
D)   third
E)   mixed

Question 14

Which of the amino acids below is unlikely to be involved in the reaction mechanism at the active site of an enzyme?

Accepted Answer

A)   alanine
B)   serine
C)   cysteine
D)   histidine
E)   aspartic acid

Question 15

How does cAMP modulate protein kinase A activity?

Accepted Answer

A)   It binds to a site on the C subunit to activate it
B)   It binds to the R subunit leading to a conformation change
C)   It causes association of the R and C subunits
D)   It causes phosphorylation of the C subunit to release the R subunit
E)   It competes with the R subunit for the active site of the C subunit

Question 16

What is the chemical difference between NAD and NADP?

Accepted Answer

A)   NADP has an additional phosphoryl group at position #2' on the pentose adjacent to adenine.
B)   NAD has a nicotinic acid moiety rather than nicotinamide.
C)   NADP has an additional phosphoryl group at position #3' on the pentose adjacent to nicotinamide.
D)   NADP has an additional phosphoryl grouping as an acyl phosphate on the nicotinic acid moiety.
E)   Chemically, they are identical.

Question 17

The Km

Accepted Answer

A)   is always a function of rate constants.
B)   can always be interpreted as a dissociation constant for the ES complex.
C)   cannot be calculated from experimental data.
D)   changes in response to noncompetitive inhibitors.
E)   changes whenever Vmax is changed experimentally.

Question 18

If one wished to diagnose myocardial infarction, one would best measure isoenzymes of

Accepted Answer

A)   creatine kinase.
B)   lactate dehydrogenase.
C)   alkaline phosphatase.
D)   all of the above.

Question 19

Which of the following could be a positive allosteric effector of an enzyme?

Accepted Answer

A)   a competitive inhibitor
B)   a noncompetitive inhibitor
C)   a compound, other than the substrate, which binds to the active site
D)   a compound, other than the substrate, which binds to the enzyme but not to the active site
E)   a coenzyme which is essential for the activity of the enzyme

Exam 10: Enzymes: Classification, Kinetics, and Control

What is one good reason why initial velocities are employed in enzyme assays?

Correct Answer
verified

In the case of an enzyme displaying a sigmoid relationship between velocity and substrate concentration, it can be concluded that

Correct Answer
verified

In the case of non-competitive inhibition, the inhibitor may bind to which of the following?

Correct Answer
verified

Which of the following could be a positive allosteric effector of an enzyme?

Correct Answer
verified

Standard free energy of a reaction can be used for all of the following EXCEPT

Correct Answer
verified

A measurement of cooperativity is the

Correct Answer
verified

The kinetics of a typical Michaelis-Menten enzyme shows what order dependence of substrate concentration at very high substrate concentrations?

Correct Answer
verified

Stereospecificity may be explained by

Correct Answer
verified

When the substrate concentration is equal to Km for a given enzyme and substrate you would expect which of the following?

Correct Answer
verified

Which of the amino acids below is unlikely to be involved in the reaction mechanism at the active site of an enzyme?

Correct Answer
verified

Which of the following statements relative to the maximum velocity (Vmax) of an enzyme catalyzed reaction (assayed under conditions of excess substrate) is correct?

Correct Answer
verified

The Km

Correct Answer
verified

Hydrolysis of high energy phosphate bonds associated with enzymatic linking of two molecules is catalyzed by what group of enzymes?

Correct Answer
verified

Enzyme cofactors

Correct Answer
verified

What is the chemical difference between NAD and NADP?

Correct Answer
verified

If one wished to diagnose myocardial infarction, one would best measure isoenzymes of

Correct Answer
verified

When enzyme rate, the constraint on the ratio of k cat/Km must be kept in mind. Which values of the two constants, respectively, will give the greatest enzyme rate at a given substrate concentration?

Correct Answer
verified

The intercept on the vertical axis (Y-axis) on a Lineweaver-Burk plot is equal to

Correct Answer
verified

How does cAMP modulate protein kinase A activity?

Correct Answer
verified

Exam 10: Enzymes: Classification, Kinetics, and Control

What is one good reason why initial velocities are employed in enzyme assays?

Correct AnswerverifiedShow Answer

In the case of an enzyme displaying a sigmoid relationship between velocity and substrate concentration, it can be concluded that

Correct AnswerverifiedShow Answer

In the case of non-competitive inhibition, the inhibitor may bind to which of the following?

Correct AnswerverifiedShow Answer

Which of the following could be a positive allosteric effector of an enzyme?

Correct AnswerverifiedShow Answer

Standard free energy of a reaction can be used for all of the following EXCEPT

Correct AnswerverifiedShow Answer

A measurement of cooperativity is the

Correct AnswerverifiedShow Answer

The kinetics of a typical Michaelis-Menten enzyme shows what order dependence of substrate concentration at very high substrate concentrations?

Correct AnswerverifiedShow Answer

Stereospecificity may be explained by

Correct AnswerverifiedShow Answer

When the substrate concentration is equal to Km for a given enzyme and substrate you would expect which of the following?

Correct AnswerverifiedShow Answer

Which of the amino acids below is unlikely to be involved in the reaction mechanism at the active site of an enzyme?

Correct AnswerverifiedShow Answer

Which of the following statements relative to the maximum velocity (Vmax) of an enzyme catalyzed reaction (assayed under conditions of excess substrate) is correct?

Correct AnswerverifiedShow Answer

The Km

Correct AnswerverifiedShow Answer

Hydrolysis of high energy phosphate bonds associated with enzymatic linking of two molecules is catalyzed by what group of enzymes?

Correct AnswerverifiedShow Answer

Enzyme cofactors

Correct AnswerverifiedShow Answer

What is the chemical difference between NAD and NADP?

Correct AnswerverifiedShow Answer

If one wished to diagnose myocardial infarction, one would best measure isoenzymes of

Correct AnswerverifiedShow Answer

When enzyme rate, the constraint on the ratio of k cat/Km must be kept in mind. Which values of the two constants, respectively, will give the greatest enzyme rate at a given substrate concentration?

Correct AnswerverifiedShow Answer

The intercept on the vertical axis (Y-axis) on a Lineweaver-Burk plot is equal to

Correct AnswerverifiedShow Answer

How does cAMP modulate protein kinase A activity?

Correct AnswerverifiedShow Answer

Correct Answer
verified

Correct Answer
verified

Correct Answer
verified

Correct Answer
verified

Correct Answer
verified

Correct Answer
verified

Correct Answer
verified

Correct Answer
verified

Correct Answer
verified

Correct Answer
verified

Correct Answer
verified

Correct Answer
verified

Correct Answer
verified

Correct Answer
verified

Correct Answer
verified

Correct Answer
verified

Correct Answer
verified

Correct Answer
verified

Correct Answer
verified