Question 1

The specificity constant is equal to

Accepted Answer

A)  [Et][S] / v0. 
B)  Km / v0. 
C)  kcat / Km. 
D)  kcat / [Et]. 
A)  [Et][S] / v0. 
B)  Km / v0. 
C)  kcat / Km. 
D)  kcat / [Et].

Question 2

What is the rate enhancement as a result of the presence of an enzyme if the uncatalyzed rate of the reaction is 1.2 * 102 mmol/sec and the catalyzed rate is 2.4 * 104 mmol/sec?

Accepted Answer

A)  0.005 
B)  200 
C)  2.88 * 106 
D)  2 
A)  0.005 
B)  200 
C)  2.88 * 106 
D)  2

Question 3

In the formation of an ESI complex, __________ inhibition can result.

Accepted Answer

A)  mixed 
B)  competitive 
C)  covalent 
D)  anticompetitive 
A)  mixed 
B)  competitive 
C)  covalent 
D)  anticompetitive

Question 4

Which of the following is a holoenzyme?

Accepted Answer

A)  pyruvate kinase with a bound K+ 
B)  alcohol dehydrogenase 
C)  nitrite reductase 
D)  hexokinase 
A)  pyruvate kinase with a bound K+ 
B)  alcohol dehydrogenase 
C)  nitrite reductase 
D)  hexokinase

Question 5

Acetylcholinesterase is an important enzyme in the nervous system. Acetylcholinesterase activity is blocked by the nerve agent sarin gas, which forms a covalent bond with a Ser in the active site of the enzyme. Sarin gas is a(n)

Accepted Answer

A)  allosteric effector. 
B)  competitive inhibitor. 
C)  reversible inhibitor. 
D)  irreversible inhibitor. 
A)  allosteric effector. 
B)  competitive inhibitor. 
C)  reversible inhibitor. 
D)  irreversible inhibitor.

Question 6

A plot of 1 / v0 versus 1/[S] is called a plot. Data in this plot have a slope equal to _.

Accepted Answer

A)  Lineweaver-Burk; Km/vmax 
B)  Lineweaver-Burk; -1/Km 
C)  Michaelis-Menten; Km/vmax 
D)  Michaelis-Menten; vmax 
A)  Lineweaver-Burk; Km/vmax 
B)  Lineweaver-Burk; -1/Km 
C)  Michaelis-Menten; Km/vmax 
D)  Michaelis-Menten; vmax

Question 7

Which type of reaction does not change the molecular formula of the product compared with that of the substrate?

Accepted Answer

A)  condensation 
B)  reduction 
C)  hydrolysis 
D)  isomerization 
A)  condensation 
B)  reduction 
C)  hydrolysis 
D)  isomerization

Question 8

Which of the following statements are true?

Accepted Answer

A)  ATCase is regulated by feedback inhibition. 
B)  CTP is an allosteric activator of ATCase. 
C)  ATP is an allosteric inhibitor of ATCase. 
D)  GTP is an allosteric inhibitor of ATCase. 
A)  ATCase is regulated by feedback inhibition. 
B)  CTP is an allosteric activator of ATCase. 
C)  ATP is an allosteric inhibitor of ATCase. 
D)  GTP is an allosteric inhibitor of ATCase.

Question 9

Consider the reaction coordinate diagram shown below. X is ; Y is .

Accepted Answer

A)  "transition state; activation energy" 
B)  "$\Delta$G‡ of catalyzed reaction; transition state" 
C)  "activation energy of catalyzed reaction; transition state" 
D)  "$\Delta$G‡ of uncatalyzed reaction; transition state" 
A)  "transition state; activation energy" 
B)  "$\Delta$G‡ of catalyzed reaction; transition state" 
C)  "activation energy of catalyzed reaction; transition state" 
D)  "$\Delta$G‡ of uncatalyzed reaction; transition state"

Question 10

An inhibitor that binds only to the ES complex and not free enzyme is known as a(n) __________ inhibitor.

Accepted Answer

A)  irreversible 
B)  competitive 
C)  uncompetitive 
D)  mixed 
A)  irreversible 
B)  competitive 
C)  uncompetitive 
D)  mixed

Question 11

Which answer correctly pairs the enzyme class with the type of reaction catalyzed?

Accepted Answer

A)  lyase; formation of two products by hydrolyzing a substrate 
B)  transferase; transfer of H or O atoms 
C)  isomerase; intramolecular rearrangements 
D)  oxidoreductase; transfer of groups within molecules 
A)  lyase; formation of two products by hydrolyzing a substrate 
B)  transferase; transfer of H or O atoms 
C)  isomerase; intramolecular rearrangements 
D)  oxidoreductase; transfer of groups within molecules

Question 12

The dihydrolipoyl transacetylase enzyme contains a lipoyl group. The lipoyl group is a(n)

Accepted Answer

A)  ion. 
B)  apoenzyme. 
C)  prosthetic group. 
D)  holo group. 
A)  ion. 
B)  apoenzyme. 
C)  prosthetic group. 
D)  holo group.

Question 13

Below is a Lineweaver-Burk plot in which the axis labels have been removed. Interpret the plot to determine the vmax.

Accepted Answer

A)  0.2 
B)  5 
C)  3 
D)  0.33 
A)  0.2 
B)  5 
C)  3 
D)  0.33

Question 14

Explain the two ways that catalytic efficiency of enzymes can be controlled within a cell.

Accepted Answer

Catalytic efficiency can be co

Question 15

Which of the following functions as a general base in the mechanism of enolase?

Accepted Answer

A)  Lys345 
B)  His57 
C)  Mg2+ 
D)  Glu211 
A)  Lys345 
B)  His57 
C)  Mg2+ 
D)  Glu211

Question 16

The mechanism of HMG-CoA reductase involves

Accepted Answer

A)  two NADPH. 
B)  one NADPH. 
C)  two NADH. 
D)  one NADH. 
A)  two NADPH. 
B)  one NADPH. 
C)  two NADH. 
D)  one NADH.

Question 17

Given the following kinetic data for the action of hexokinase for two different substrates (glucose and fructose), determine which is the preferred substrate of the enzyme and explain your answer.

Accepted Answer

Glucose is the preferred substrate for h

Question 18

The transition state of a reaction is

Accepted Answer

A)  higher in free energy than the product. 
B)  lower in free energy than the ground state of the substrate. 
C)  easily isolated. 
D)  equal to the $\Delta$G‡ of the uncatalyzed reaction minus the $\Delta$G‡ of the catalyzed reaction. 
A)  higher in free energy than the product. 
B)  lower in free energy than the ground state of the substrate. 
C)  easily isolated. 
D)  equal to the $\Delta$G‡ of the uncatalyzed reaction minus the $\Delta$G‡ of the catalyzed reaction.

Question 19

Which of the following is true of the tetrahedral intermediate in the chymotrypsin mechanism?

Accepted Answer

A)  It is lower in free energy than the substrate. 
B)  It is partially positively charged. 
C)  All bonds are the same length. 
D)  It contains an oxyanion. 
A)  It is lower in free energy than the substrate. 
B)  It is partially positively charged. 
C)  All bonds are the same length. 
D)  It contains an oxyanion.

Question 20

On a plot of [product] versus time for an enzyme-catalyzed reaction, the v0 is equal to the

Accepted Answer

A)  slope of the line / [S]. 
B)  [P] at the lowest time point. 
C)  slope of the line. 
D)  y-intercept. 
A)  slope of the line / [S]. 
B)  [P] at the lowest time point. 
C)  slope of the line. 
D)  y-intercept.

Exam 7: Enzyme Mechanisms

The specificity constant is equal to

What is the rate enhancement as a result of the presence of an enzyme if the uncatalyzed rate of the reaction is 1.2 * 102 mmol/sec and the catalyzed rate is 2.4 * 104 mmol/sec?

In the formation of an ESI complex, __________ inhibition can result.

Which of the following is a holoenzyme?

Acetylcholinesterase is an important enzyme in the nervous system. Acetylcholinesterase activity is blocked by the nerve agent sarin gas, which forms a covalent bond with a Ser in the active site of the enzyme. Sarin gas is a(n)

A plot of 1 / v0 versus 1/[S] is called a plot. Data in this plot have a slope equal to _.

Which type of reaction does not change the molecular formula of the product compared with that of the substrate?

Which of the following statements are true?

Consider the reaction coordinate diagram shown below. X is ; Y is .

An inhibitor that binds only to the ES complex and not free enzyme is known as a(n) __________ inhibitor.

Which answer correctly pairs the enzyme class with the type of reaction catalyzed?

The dihydrolipoyl transacetylase enzyme contains a lipoyl group. The lipoyl group is a(n)

Below is a Lineweaver-Burk plot in which the axis labels have been removed. Interpret the plot to determine the vmax.

Explain the two ways that catalytic efficiency of enzymes can be controlled within a cell.

Which of the following functions as a general base in the mechanism of enolase?

The mechanism of HMG-CoA reductase involves

Given the following kinetic data for the action of hexokinase for two different substrates (glucose and fructose), determine which is the preferred substrate of the enzyme and explain your answer.

The transition state of a reaction is

Which of the following is true of the tetrahedral intermediate in the chymotrypsin mechanism?

On a plot of [product] versus time for an enzyme-catalyzed reaction, the v0 is equal to the

Principles of Biochemistry

Physical Biochemistry: Energy Conversion, Water, and Membranes

Nucleic Acid Structure and Function

Protein Structure

Methods in Protein Biochemistry

Protein Function

Cell Signaling Systems

Glycolysis: a Paradigm of Metabolic Regulation

The Citrate Cycle

Oxidative Phosphorylation

Photosynthesis

Carbohydrate Structure and Function

Carbohydrate Metabolism

Lipid Structure and Function

Lipid Metabolism

Amino Acid Metabolism

Nucleotide Metabolism

Metabolic Integration

DNA Replication, Repair, and Recombination

RNA Synthesis, Processing, and Gene Silencing

Protein Synthesis, Posttranslational Modification, and Transport

Gene Regulation

Filters

What is the rate enhancement as a result of the presence of an enzyme if the uncatalyzed rate of the reaction is 1.2 * 10²mmol/sec and the catalyzed rate is 2.4 * 10⁴mmol/sec?

A plot of 1 / v₀ versus 1/[S] is called a plot. Data in this plot have a slope equal to _.

Below is a Lineweaver-Burk plot in which the axis labels have been removed. Interpret the plot to determine the v_max.

On a plot of [product] versus time for an enzyme-catalyzed reaction, the v₀ is equal to the