Question 1

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 2

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 3

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

Accepted Answer

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

Question 4

Which of the following is NOT a function of the Mg2+ ions in the mechanism of enolase?

Accepted Answer

A)  orientation of substrate in the active site 
B)  stabilizing the intermediate 
C)  making the proton at the C-2 position more acidic 
D)  electrophilic attack on the scissile bond 
A)  orientation of substrate in the active site 
B)  stabilizing the intermediate 
C)  making the proton at the C-2 position more acidic 
D)  electrophilic attack on the scissile bond

Question 5

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 6

Consider the reaction coordinate diagram shown below for the conversion of substrate (S)to product (P).Assume that a hypothetical enzyme is added that destabilizes the substrate (S)so that it has the free energy of S*,but otherwise the reaction is the same (in other words,it still goes through the transition state indicated in the diagram).Justify why the hypothetical enzyme is a catalyst.

Accepted Answer

The role of a catalyst is to lower the a

Question 7

Phosphorylation of __________ in glycogen phosphorylase shifts the enzyme to the __________.

Accepted Answer

A)  Tyr397; T state 
B)  Tyr397; R state 
C)  Ser14; T state 
D)  Ser14; R state 
A)  Tyr397; T state 
B)  Tyr397; R state 
C)  Ser14; T state 
D)  Ser14; R state

Question 8

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 9

For a reaction of S   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 10

The conversion of 2-phosphoglycerate to phosphoenolpyruvate is an example of which type of reaction?

Accepted Answer

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

Question 11

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 12

Hexokinase catalyzes the phosphorylation of glucose to glucose 6-phosphate.Hexokinase belongs to which enzyme class?

Accepted Answer

A)  transferase 
B)  ligase 
C)  oxidoreductase 
D)  hydrolase 
A)  transferase 
B)  ligase 
C)  oxidoreductase 
D)  hydrolase

Question 13

The three general categories of enzyme-mediated reactions,which are determined on the basis of the work they accomplish,include all EXCEPT

Accepted Answer

A)  coenzyme-dependent redox reactions. 
B)  reversible covalent modification. 
C)  hydrophobic collapse reactions. 
D)  metabolite transformation reactions. 
A)  coenzyme-dependent redox reactions. 
B)  reversible covalent modification. 
C)  hydrophobic collapse reactions. 
D)  metabolite transformation reactions.

Question 14

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 15

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 16

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 17

Enzymes from four different species catalyze the same reaction.Based on the reaction coordinate diagrams below,which species contains an enzyme that experiences more bonding interactions with the transition state of the reaction?

Accepted Answer

A)  species A 
B)  species B 
C)  species C 
D)  species D 
A)  species A 
B)  species B 
C)  species C 
D)  species D

Question 18

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 19

The hemithioacetal intermediate formed during the action of HMG-CoA reductase is stabilized by

Accepted Answer

A)  Lys267. 
B)  Asp283. 
C)  His381. 
D)  Glu83. 
A)  Lys267. 
B)  Asp283. 
C)  His381. 
D)  Glu83.

Question 20

Below is a ribbon diagram of an enzyme.Four regions of the enzyme are indicated.Which is most likely the active site?

Accepted Answer

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

Exam 7: Enzyme Mechanisms

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

Which of the following is a holoenzyme?

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

Which of the following is NOT a function of the Mg2+ ions in the mechanism of enolase?

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

Phosphorylation of __________ in glycogen phosphorylase shifts the enzyme to the __________.

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

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

The conversion of 2-phosphoglycerate to phosphoenolpyruvate is an example of which type of reaction?

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

Hexokinase catalyzes the phosphorylation of glucose to glucose 6-phosphate.Hexokinase belongs to which enzyme class?

The three general categories of enzyme-mediated reactions,which are determined on the basis of the work they accomplish,include all EXCEPT

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

Which of the following is a prosthetic group?

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

Enzymes from four different species catalyze the same reaction.Based on the reaction coordinate diagrams below,which species contains an enzyme that experiences more bonding interactions with the transition state of the reaction?

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

The hemithioacetal intermediate formed during the action of HMG-CoA reductase is stabilized by

Below is a ribbon diagram of an enzyme.Four regions of the enzyme are indicated.Which is most likely the active site?

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

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

Which of the following is NOT a function of the Mg²⁺ ions in the mechanism of enolase?

Phosphorylation of in glycogen phosphorylase shifts the enzyme to the .

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