Question 1

Which equilibrium below applies to noncompetitive inhibition?

Accepted Answer

A)   I
B)   II
C)   III
D)   IVE) C) and D)
F) All of the above

Question 2

Oxidases, peroxidases, oxygenases or reductases are all

Accepted Answer

A)   lyases.
B)   synthases.
C)   synthetases.
D)   oxidoreductases.
E)   hydrolases.F) A) and B)
G) A) and C)

Question 3

It is difficult to determine either Km or Vmax from a graph of velocity vs. substrate concentration because

Accepted Answer

A)   too much substrate is required to determine them.
B)   the graph is sigmoidal.
C)   an asymptotic value must be determined from the graph.
D)   the points on the graph are often not spread out on the hyperbola.E) A) and B)
F) A) and C)

Question 4

Unlike typical catalyzed reactions in organic chemistry enzyme reactions are

Accepted Answer

A)   usually stereospecific.
B)   reaction specific.
C)   essentially 100% efficient.
D)   modulated to change activity levels.
E)   All of the aboveF) B) and D)
G) B) and E)

Question 5

When varying the substrate concentration at a fixed concentration of enzyme it is observed that at low concentrations of substrate the reaction is ,while at high concentrations of substrate the reaction is .

Accepted Answer

A)   maximal; initial
B)   initial; maximal
C)   second order; first order
D)   first order; second order
E)   first order; zero orderF) A) and E)
G) C) and D)

Question 6

Most of the known enzymes are .

Accepted Answer

A)   oxidoreductases
B)   transferases
C)   hydrolases
D)   lyases
E)   isomerasesF) A) and E)
G) None of the above

Question 7

Phosphorylation that changes an enzymeʹs activity is an example of .

Accepted Answer

A)   covalent modification
B)   allosteric regulation
C)   sequential modification
D)   site-directed mutagenesisE) A) and C)
F) C) and D)

Question 8

When two different substrates react to form two different products, the rate constants for each separate substrate can be determined by

Accepted Answer

A)   varying one substrate at a time, keeping the other in excess.
B)   varying both substrates and measuring the appearance of the two products.
C)   limiting one substrate and varying the other.
D)   keeping both substrate concentrations high and detecting one product at a time.E) B) and C)
F) A) and D)

Question 9

Which statement is false about covalent modification?

Accepted Answer

A)   It is reversible.
B)   It is slightly slower than allosteric regulation.
C)   It usually uses the same enzyme for activation and inactivation.
D)   All of the aboveE) B) and C)
F) A) and C)

Question 10

Which enzyme below is fastest?

Accepted Answer

A)   kinase, kcat = 103 
B)   papain, kcat = 10
C)   carboxypeptidase, kcat = 102 
D)   catalase, kcat = 107E) A) and C)
F) A) and B)

Question 11

Affinity labels are radioactive competitive inhibitors used to identify the most important residues in an enzymeʹs active site.

Accepted Answer

A) True 
 B)False

Question 12

An inhibitor binds to a site other than the active site of the enzyme. Which statement below correlates with this observation?

Accepted Answer

A)   It must be a competitive inhibitor.
B)   The inhibition must be irreversible.
C)   It could be noncompetitive or uncompetitive inhibition.
D)   It could be irreversible, competitive, noncompetitive or uncompetitive. The data do not relate to the type of inhibition.E) B) and C)
F) None of the above

Question 13

Which is not an explanation of why site-directed mutagenesis is a more powerful tool than many other techniques for determining important residues in an enzyme?

Accepted Answer

A)   It is a more specific technique than irreversible inhibition experiments.
B)   It can be used on enzymes for which no specific irreversible inhibitor is known.
C)   It allows for testing of the specific function of amino acid side chains in an enzyme.
D)   It is especially useful for enzymes whose sequence is not known.E) None of the above
F) C) and D)

Question 14

What type of inhibition is indicated by the data graphed below?

Accepted Answer

A)   competitive
B)   uncompetitive
C)   noncompetitive
D)   irreversibleE) A) and C)
F) B) and C)

Question 15

At sufficiently high substrate concentration all types of reversible inhibition can be overwhelmed. At high substrate concentration the enzyme will be saturated and the reaction will proceed at the same maximum velocity as in the absence of inhibitor.

Accepted Answer

A) True 
 B)False

Question 16

The concentrations of enzymes are determined by using pseudo first-order conditions in which

Accepted Answer

A)   S concentration is kept the same and the rate is measured.
B)   E concentration is kept the same and the rate is measured.
C)   S concentration is constant, E concentration varied and the rate is measured.
D)   E concentration is constant, S concentration varied and the rate is measured.
E)   All of the aboveF) All of the above
G) A) and B)

Question 17

Select the correct class of enzyme for each of these reactions. A) isomerase
B) ligase
C) lyase
D) transferase
E) oxidoreductase
F) hydrolase
-L-aspartic acid +
a-ketoglutarate → oxaloacetic acid + L-Glutamate

Accepted Answer

The answer of Select the correct class of enzyme for...

Question 18

The hydrophobic cleft in globular proteins which bind substrate molecules is called the .

Accepted Answer

A)   substrate pocket
B)   modulator site
C)   active site
D)   activity site
E)   oligomeric siteF) A) and C)
G) A) and D)

Question 19

The most common enzyme inhibitors are competitive inhibitors.

Accepted Answer

A) True 
 B)False

Question 20

Which of the following statements is FALSE?

Accepted Answer

A)   Enzymes make reactions 103 to 1020 times faster.
B)   Enzymes lower the amount of energy needed for a reaction.
C)   Enzymes are chemically unchanged during the actual catalytic process.
D)   Enzymes speed up the attainment of a reaction equilibrium.
E)   Enzymes are proteins.F) A) and B)
G) C) and E)

Exam 5: Properties of Enzymes

Oxidases, peroxidases, oxygenases or reductases are all

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Affinity labels are radioactive competitive inhibitors used to identify the most important residues in an enzymeʹs active site.

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The hydrophobic cleft in globular proteins which bind substrate molecules is called the .

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When varying the substrate concentration at a fixed concentration of enzyme it is observed that at low concentrations of substrate the reaction is ,while at high concentrations of substrate the reaction is .

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Which of the following statements is FALSE?

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Which equilibrium below applies to noncompetitive inhibition?

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The concentrations of enzymes are determined by using pseudo first-order conditions in which

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Unlike typical catalyzed reactions in organic chemistry enzyme reactions are

Correct AnswerverifiedShow Answer

Which is not an explanation of why site-directed mutagenesis is a more powerful tool than many other techniques for determining important residues in an enzyme?

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Which enzyme below is fastest?

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An inhibitor binds to a site other than the active site of the enzyme. Which statement below correlates with this observation?

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Which statement is false about covalent modification?

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The most common enzyme inhibitors are competitive inhibitors.

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It is difficult to determine either Km or Vmax from a graph of velocity vs. substrate concentration because

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Most of the known enzymes are .

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Phosphorylation that changes an enzymeʹs activity is an example of .

Correct AnswerverifiedShow Answer

When two different substrates react to form two different products, the rate constants for each separate substrate can be determined by

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Select the correct class of enzyme for each of these reactions. A) isomerase B) ligase C) lyase D) transferase E) oxidoreductase F) hydrolase -L-aspartic acid + a-ketoglutarate → oxaloacetic acid + L-Glutamate

Correct AnswerverifiedShow Answer

What type of inhibition is indicated by the data graphed below?

Correct AnswerverifiedShow Answer

At sufficiently high substrate concentration all types of reversible inhibition can be overwhelmed. At high substrate concentration the enzyme will be saturated and the reaction will proceed at the same maximum velocity as in the absence of inhibitor.

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It is difficult to determine either K_mor V_maxfrom a graph of velocity vs. substrate concentration because

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