Question 1

Which answer correctly classifies the compound with its relationship to aspartate transcarbamoylase?

Accepted Answer

A)  ATP; allosteric inhibitor 
B)  ATP; allosteric activator 
C)  CTP; allosteric activator 
D)  CTP; substrate 
A)  ATP; allosteric inhibitor 
B)  ATP; allosteric activator 
C)  CTP; allosteric activator 
D)  CTP; substrate

Question 2

The side chains of the amino acids that make up the catalytic triad of chymotrypsin contain all EXCEPT

Accepted Answer

A)  a hydroxyl group. 
B)  a carboxylic acid. 
C)  an aromatic group. 
D)  an imidazole. 
A)  a hydroxyl group. 
B)  a carboxylic acid. 
C)  an aromatic group. 
D)  an imidazole.

Question 3

In the steady-state condition assumed in Michaelis-Menten kinetics, is relatively constant.

Accepted Answer

A)  [ES] 
B)  [S] 
C)  v0 
D)  [ES] / [S] 
A)  [ES] 
B)  [S] 
C)  v0 
D)  [ES] / [S]

Question 4

Which type of interaction is more likely to be found between an enzyme and an irreversible inhibitor?

Accepted Answer

A)  covalent bond 
B)  hydrogen bond 
C)  ionic interaction 
D)  van der Waals interaction 
A)  covalent bond 
B)  hydrogen bond 
C)  ionic interaction 
D)  van der Waals interaction

Question 5

In a reversible covalent modification reaction involving the phosphorylation of a target protein, which of the following amino acids is LEAST likely to be modified with a phosphate group?

Accepted Answer

A)  Ser 
B)  Phe 
C)  Tyr 
D)  Thr 
A)  Ser 
B)  Phe 
C)  Tyr 
D)  Thr

Question 6

The initial velocity of an enzyme-catalyzed reaction is followed at various substrate concentrations. At very high substrate concentrations it is observed that the initial velocity no longer increases as more substrate is added. The velocity under these conditions is known as

Accepted Answer

A)  "the ultimate velocity." 
B)  "the maximum velocity." 
C)  "v[S]." 
D)  "optimal velocity." 
A)  "the ultimate velocity." 
B)  "the maximum velocity." 
C)  "v[S]." 
D)  "optimal velocity."

Question 7

Which of the following is a way that an enzyme can increase the rate of a reaction inside a cell?

Accepted Answer

A)  increasing the temperature of the cell 
B)  increasing the pressure inside the cell 
C)  increasing the substrate concentration inside the cell 
D)  orienting substrates appropriately for the reaction to occur 
A)  increasing the temperature of the cell 
B)  increasing the pressure inside the cell 
C)  increasing the substrate concentration inside the cell 
D)  orienting substrates appropriately for the reaction to occur

Question 8

When a nucleophile present in the enzyme attacks an electrophilic substrate to form an enzyme-substrate intermediate, this is an example of catalysis.

Accepted Answer

A)  covalent 
B)  acid-base 
C)  metal ion 
D)  hydrophobic 
A)  covalent 
B)  acid-base 
C)  metal ion 
D)  hydrophobic

Question 9

Which of the following is an assumption made when using Michaelis-Menten kinetics?

Accepted Answer

A)  The conversion of E + P $\rightarrow$ ES does not occur. 
B)  k1 > k2 
C)  v0 = vmax at low [S] 
D)  The conversion of EP $\rightarrow$ E + P is rapid. 
A)  The conversion of E + P $\rightarrow$ ES does not occur. 
B)  k1 > k2 
C)  v0 = vmax at low [S] 
D)  The conversion of EP $\rightarrow$ E + P is rapid.

Question 10

What is the appropriate order of the following steps? 
A. Glutamine binding to uridylyltransferase
B. Adenylation of glutamine synthetase
C. Deuridylation of glutamine synthetase adenylyltransferase

Accepted Answer

A)  C, B, A 
B)  A, C, B 
C)  A, B, C 
D)  C, A, B 
A)  C, B, A 
B)  A, C, B 
C)  A, B, C 
D)  C, A, B

Question 11

Which of the following pairs correctly matches the type of interaction observed between an inhibitor and an enzyme with the type of inhibition?

Accepted Answer

A)  ionic; irreversible 
B)  covalent; irreversible 
C)  hydrogen bonding; reversible 
D)  hydrophobic; irreversible 
A)  ionic; irreversible 
B)  covalent; irreversible 
C)  hydrogen bonding; reversible 
D)  hydrophobic; irreversible

Question 12

Which of the following is NOT a primary mechanism that affects catalytic efficiency?

Accepted Answer

A)  binding of regulatory molecules 
B)  covalent modification 
C)  proteolytic processing 
D)  cofactor degradation 
A)  binding of regulatory molecules 
B)  covalent modification 
C)  proteolytic processing 
D)  cofactor degradation

Question 13

The substrate binding pocket of __________ contains a(n) __________, which facilitates substrate specificity.

Accepted Answer

A)  trypsin; Ser 
B)  chymotrypsin; Asp 
C)  trypsin; Asp 
D)  elastase; Gly 
A)  trypsin; Ser 
B)  chymotrypsin; Asp 
C)  trypsin; Asp 
D)  elastase; Gly

Question 14

A mutation of Lys229 in aldolase leads to a loss of enzyme activity. This is most likely because the

Accepted Answer

A)  active site can no longer exclude water. 
B)  active site can no longer include water. 
C)  enzyme can no longer hold the intermediate in the correct orientation for catalysis. 
D)  product will remain bound to the enzyme active site. 
A)  active site can no longer exclude water. 
B)  active site can no longer include water. 
C)  enzyme can no longer hold the intermediate in the correct orientation for catalysis. 
D)  product will remain bound to the enzyme active site.

Question 15

Which of the following is true of a coenzyme but NOT true of a prosthetic group?

Accepted Answer

A)  It contains an organic component. 
B)  It is loosely associated with the enzyme. 
C)  It is necessary for enzyme function. 
D)  It is present in a holoenzyme but not an apoenzyme. 
A)  It contains an organic component. 
B)  It is loosely associated with the enzyme. 
C)  It is necessary for enzyme function. 
D)  It is present in a holoenzyme but not an apoenzyme.

Question 16

When __________ is increased, is activated, which acts on glycogen phosphorylase, leading to a decrease in the activity of the enzyme.

Accepted Answer

A)  glucagon; phosphorylase kinase 
B)  epinephrine; phosphorylase kinase 
C)  insulin; protein phosphatase 1 
D)  glucagon; protein phosphatase 1 
A)  glucagon; phosphorylase kinase 
B)  epinephrine; phosphorylase kinase 
C)  insulin; protein phosphatase 1 
D)  glucagon; protein phosphatase 1

Question 17

Hexokinase catalyzes the first step of glycolysis, which occurs in the cell cytoplasm. The protocol for an in vitro enzyme activity assay of hexokinase suggests that the assay is carried out at a pH of 7.4. Predict what may occur if the assay is carried out at a pH of 8.8 instead. Explain your reasoning.

Accepted Answer

The enzyme activity would be l

Question 18

Which of the following is a prosthetic group?

Accepted Answer

A)  Mg2+ 
B)  NADH 
C)  Zn2+ 
D)  heme 
A)  Mg2+ 
B)  NADH 
C)  Zn2+ 
D)  heme

Question 19

A reaction coordinate diagram comparing an uncatalyzed reaction with an enzyme-catalyzed reaction can directly illustrate that the enzyme , but will not directly illustrate that the enzyme _.

Accepted Answer

A)  orients the substrates appropriately for the reaction to occur; provides an alternative path for product formation 
B)  provides an alternative path for product formation; stabilizes the transition state 
C)  stabilizes the transition state; orients the substrates appropriately for the reaction to occur 
D)  stabilizes the transition state; provides an alternative path for product formation 
A)  orients the substrates appropriately for the reaction to occur; provides an alternative path for product formation 
B)  provides an alternative path for product formation; stabilizes the transition state 
C)  stabilizes the transition state; orients the substrates appropriately for the reaction to occur 
D)  stabilizes the transition state; provides an alternative path for product formation

Question 20

A mixture of enzyme and inhibitor is run through a size-exclusion chromatography column. The activity of the enzyme is assessed before and after the chromatography. The enzyme has more activity after the chromatography step. Which of the following is true?

Accepted Answer

A)  The enzyme was not eluted fully from the column. 
B)  The enzyme was denatured during chromatography. 
C)  The inhibitor is a reversible inhibitor. 
D)  The inhibitor is an irreversible inhibitor. 
A)  The enzyme was not eluted fully from the column. 
B)  The enzyme was denatured during chromatography. 
C)  The inhibitor is a reversible inhibitor. 
D)  The inhibitor is an irreversible inhibitor.

Exam 7: Enzyme Mechanisms

Which answer correctly classifies the compound with its relationship to aspartate transcarbamoylase?

The side chains of the amino acids that make up the catalytic triad of chymotrypsin contain all EXCEPT

In the steady-state condition assumed in Michaelis-Menten kinetics, is relatively constant.

Which type of interaction is more likely to be found between an enzyme and an irreversible inhibitor?

In a reversible covalent modification reaction involving the phosphorylation of a target protein, which of the following amino acids is LEAST likely to be modified with a phosphate group?

The initial velocity of an enzyme-catalyzed reaction is followed at various substrate concentrations. At very high substrate concentrations it is observed that the initial velocity no longer increases as more substrate is added. The velocity under these conditions is known as

Which of the following is a way that an enzyme can increase the rate of a reaction inside a cell?

When a nucleophile present in the enzyme attacks an electrophilic substrate to form an enzyme-substrate intermediate, this is an example of catalysis.

Which of the following is an assumption made when using Michaelis-Menten kinetics?

What is the appropriate order of the following steps? A. Glutamine binding to uridylyltransferase B. Adenylation of glutamine synthetase C. Deuridylation of glutamine synthetase adenylyltransferase

Which of the following pairs correctly matches the type of interaction observed between an inhibitor and an enzyme with the type of inhibition?

Which of the following is NOT a primary mechanism that affects catalytic efficiency?

The substrate binding pocket of __________ contains a(n) __________, which facilitates substrate specificity.

A mutation of Lys229 in aldolase leads to a loss of enzyme activity. This is most likely because the

Which of the following is true of a coenzyme but NOT true of a prosthetic group?

When __________ is increased, is activated, which acts on glycogen phosphorylase, leading to a decrease in the activity of the enzyme.

Which of the following is a prosthetic group?

A reaction coordinate diagram comparing an uncatalyzed reaction with an enzyme-catalyzed reaction can directly illustrate that the enzyme , but will not directly illustrate that the enzyme _.

A mixture of enzyme and inhibitor is run through a size-exclusion chromatography column. The activity of the enzyme is assessed before and after the chromatography. The enzyme has more activity after the chromatography step. Which of the following is true?

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

The substrate binding pocket of contains a(n) , which facilitates substrate specificity.

A mutation of Lys₂₂₉ in aldolase leads to a loss of enzyme activity. This is most likely because the