Question 1

A mutation results in the change of Ser to Asp in the substrate binding pocket of chymotrypsin. Most likely, the mutant enzyme will

Accepted Answer

A)  no longer catalyze the hydrolysis of a peptide bond because Asp cannot facilitate the nucleophilic attack. 
B)  no longer catalyze the hydrolysis of a peptide bond because Asp is unable to be deprotonated by His57. 
C)  preferentially hydrolyze substrates containing phenylalanine. 
D)  preferentially hydrolyze substrates containing lysine. 
A)  no longer catalyze the hydrolysis of a peptide bond because Asp cannot facilitate the nucleophilic attack. 
B)  no longer catalyze the hydrolysis of a peptide bond because Asp is unable to be deprotonated by His57. 
C)  preferentially hydrolyze substrates containing phenylalanine. 
D)  preferentially hydrolyze substrates containing lysine.

Question 2

Describe two conformational changes that occur when aspartate transcarbamoylase shifts from the R state to the T state.

Accepted Answer

The catalytic subuni

Question 3

If an enzyme carries out acid-base catalysis, which of the following amino acids could act as general acid?

Accepted Answer

A)  phenylalanine 
B)  glycine 
C)  histidine 
D)  alanine 
A)  phenylalanine 
B)  glycine 
C)  histidine 
D)  alanine

Question 4

The substrate binding pocket of is best at accommodating substrates with small side chains.

Accepted Answer

A)  elastase 
B)  chymotrypsin 
C)  enolase 
D)  trypsin 
A)  elastase 
B)  chymotrypsin 
C)  enolase 
D)  trypsin

Question 5

What is Henry Eyring's transition state theory?

Accepted Answer

Henry Eyring's transition state theory s

Question 6

A plot of vo versus [S] for aspartyl transcarbamoylase displays three sigmoidal lines. If the line in the middle represents the enzyme activity in the absence of any allosteric effectors, then the line to the __________ represents the enzyme in the __________ when bound to __________.

Accepted Answer

A)  right; R state; CTP 
B)  right; T state; CTP 
C)  left; R state; GTP 
D)  left; T state; GTP 
A)  right; R state; CTP 
B)  right; T state; CTP 
C)  left; R state; GTP 
D)  left; T state; GTP

Question 7

Both the substrate and the tetrahedral intermediate, when associated with chymotrypsin,

Accepted Answer

A)  contain an oxyanion. 
B)  interact with the oxyanion hole. 
C)  undergo a nucleophilic attack. 
D)  hydrogen bond to Asp102. 
A)  contain an oxyanion. 
B)  interact with the oxyanion hole. 
C)  undergo a nucleophilic attack. 
D)  hydrogen bond to Asp102.

Question 8

Complete the following statement: The NH groups of Ser195 and Gly193 in chymotrypsin are able to stabilize the intermediate of the reaction by

Accepted Answer

forming hy

Question 9

An enzyme can increase the rate of a reaction inside a cell by the energy of the __________.

Accepted Answer

A)  lowering; transition state 
B)  increasing; product 
C)  lowering; substrate 
D)  increasing; transition state 
A)  lowering; transition state 
B)  increasing; product 
C)  lowering; substrate 
D)  increasing; transition state

Question 10

Refer to the reaction coordinate diagram below. The change in the activation energy of the reaction because of the presence of an enzyme is illustrated by the energy of minus the energy of _.

Accepted Answer

A)  B; A 
B)  B; C 
C)  B; D 
D)  C; D 
A)  B; A 
B)  B; C 
C)  B; D 
D)  C; D

Question 11

All of the following are common catalytic reaction mechanisms in enzyme active sites EXCEPT catalysis.

Accepted Answer

A)  acid-base 
B)  covalent 
C)  metal ion 
D)  van der Waals 
A)  acid-base 
B)  covalent 
C)  metal ion 
D)  van der Waals

Question 12

For a reaction of S $\rightarrow$ P, the rate constant of the reaction is equal to

Accepted Answer

A)  "k." 
B)  "-k." 
C)  "1 / v." 
D)  "[S] / v." 
A)  "k." 
B)  "-k." 
C)  "1 / v." 
D)  "[S] / v."

Question 13

Which amino acid acts as a general acid and a general base in the mechanism of chymotrypsin?

Accepted Answer

A)  Ser195 
B)  His57 
C)  Gly193 
D)  Asp102 
A)  Ser195 
B)  His57 
C)  Gly193 
D)  Asp102

Question 14

In the figure below, KM is indicated at

Accepted Answer

A)  A. 
B)  B. 
C)  C. 
D)  D. 
A)  A. 
B)  B. 
C)  C. 
D)  D.

Question 15

An enzyme that requires the coenzyme nicotinamide adenine dinucleotide belongs to which enzyme class?

Accepted Answer

A)  transferases 
B)  isomerases 
C)  ligases 
D)  oxidoreductases 
A)  transferases 
B)  isomerases 
C)  ligases 
D)  oxidoreductases

Question 16

The y-axis of a Lineweaver-Burk plot is

Accepted Answer

A)  v0. 
B)  1 / vo. 
C)  Km / vmax. 
D)  1 / [S]. 
A)  v0. 
B)  1 / vo. 
C)  Km / vmax. 
D)  1 / [S].

Question 17

A plot of v0 versus substrate concentration for aspartate transcarbamoylase displays a sigmoidal curve. Explain how the plot would change in the presence of CTP.

Accepted Answer

CTP is an allosteric inhibitor

Question 18

Place the following HMG-CoA reductase steps in the correct order: 
A. Reduction of aldehyde
B. Breakdown of hemithioacetal
C. Reduction of thioester
D. Cofactor exchange

Accepted Answer

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

Question 19

Binding of glucose to hexokinase causes a conformational change in the enzyme. This is an example of the __________ model of enzyme catalysis.

Accepted Answer

A)  substrate-induced 
B)  lock and key 
C)  induced-fit 
D)  glove and hand 
A)  substrate-induced 
B)  lock and key 
C)  induced-fit 
D)  glove and hand

Question 20

When compared with the T state of aspartate transcarbamoylase, the R state

Accepted Answer

A)  has dissociated into two C3R3 complexes. 
B)  has greater separation of the catalytic subunits. 
C)  is bound to CTP. 
D)  has substrate bound in the ATP binding site. 
A)  has dissociated into two C3R3 complexes. 
B)  has greater separation of the catalytic subunits. 
C)  is bound to CTP. 
D)  has substrate bound in the ATP binding site.

Exam 7: Enzyme Mechanisms

A mutation results in the change of Ser to Asp in the substrate binding pocket of chymotrypsin. Most likely, the mutant enzyme will

Describe two conformational changes that occur when aspartate transcarbamoylase shifts from the R state to the T state.

If an enzyme carries out acid-base catalysis, which of the following amino acids could act as general acid?

The substrate binding pocket of is best at accommodating substrates with small side chains.

What is Henry Eyring's transition state theory?

A plot of vo versus [S] for aspartyl transcarbamoylase displays three sigmoidal lines. If the line in the middle represents the enzyme activity in the absence of any allosteric effectors, then the line to the __________ represents the enzyme in the __________ when bound to __________.

Both the substrate and the tetrahedral intermediate, when associated with chymotrypsin,

Complete the following statement: The NH groups of Ser195 and Gly193 in chymotrypsin are able to stabilize the intermediate of the reaction by

An enzyme can increase the rate of a reaction inside a cell by the energy of the __________.

Refer to the reaction coordinate diagram below. The change in the activation energy of the reaction because of the presence of an enzyme is illustrated by the energy of minus the energy of _.

All of the following are common catalytic reaction mechanisms in enzyme active sites EXCEPT catalysis.

For a reaction of S →\rightarrow→ P, the rate constant of the reaction is equal to

Which amino acid acts as a general acid and a general base in the mechanism of chymotrypsin?

In the figure below, KM is indicated at

An enzyme that requires the coenzyme nicotinamide adenine dinucleotide belongs to which enzyme class?

The y-axis of a Lineweaver-Burk plot is

A plot of v0 versus substrate concentration for aspartate transcarbamoylase displays a sigmoidal curve. Explain how the plot would change in the presence of CTP.

Place the following HMG-CoA reductase steps in the correct order: A. Reduction of aldehyde B. Breakdown of hemithioacetal C. Reduction of thioester D. Cofactor exchange

Binding of glucose to hexokinase causes a conformational change in the enzyme. This is an example of the __________ model of enzyme catalysis.

When compared with the T state of aspartate transcarbamoylase, the R state

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

A plot of v_o versus [S] for aspartyl transcarbamoylase displays three sigmoidal lines. If the line in the middle represents the enzyme activity in the absence of any allosteric effectors, then the line to the represents the enzyme in the when bound to __.

For a reaction of S $\rightarrow$ P, the rate constant of the reaction is equal to

In the figure below, K_M is indicated at

A plot of v₀ versus substrate concentration for aspartate transcarbamoylase displays a sigmoidal curve. Explain how the plot would change in the presence of CTP.