Question 1

Zymogens are often active only in the environment in which they are functional.

Accepted Answer

A) True 
 B)False

Question 2

Transition state analogs should

Accepted Answer

A) stabilize transition states. 
B) have a dissociation constant of 10-¹³ M or less. 
C) bind very tightly to the enzyme. 
D) A and C. 
E) B and C. 
A) stabilize transition states. 
B) have a dissociation constant of 10-¹³ M or less. 
C) bind very tightly to the enzyme. 
D) A and C. 
E) B and C.

Question 3

Match each of these terms with the correct description:
-Rely on amino acid side chains that can donate and accept protons at nearly neutral pH

Accepted Answer

A) induced fit 
B) proximity effect 
C) covalent catalysis 
D) diffusion-controlled reaction 
E) acid-base catalysis 
A) induced fit 
B) proximity effect 
C) covalent catalysis 
D) diffusion-controlled reaction 
E) acid-base catalysis

Question 4

An update of Fischer's lock-and-key theory of enzyme specificity views the ________ as the lock and ________ as the key.

Accepted Answer

A) enzyme;substrate 
B) substrate;enzyme 
C) enzyme;transition state 
D) transition state;enzyme 
E) substrate;transition state 
A) enzyme;substrate 
B) substrate;enzyme 
C) enzyme;transition state 
D) transition state;enzyme 
E) substrate;transition state

Question 5

A key role of the hydroxyl group at position 6 in the purine ring in the formation of a transition state by the enzyme adenosine deaminase is obtained by comparing a ________ and a ________.

Accepted Answer

A) competitive inhibitor;noncompetitive inhibitor 
B) transition state analog;normal substrate 
C) noncompetitive inhibitor;transition state analog 
D) competitive inhibitor;transition state analog 
E) All of the above. 
A) competitive inhibitor;noncompetitive inhibitor 
B) transition state analog;normal substrate 
C) noncompetitive inhibitor;transition state analog 
D) competitive inhibitor;transition state analog 
E) All of the above.

Question 6

Match each of these terms with the correct description:
-Correct positioning of two reacting groups at the active site

Accepted Answer

A) induced fit 
B) proximity effect 
C) covalent catalysis 
D) diffusion-controlled reaction 
E) acid-base catalysis 
A) induced fit 
B) proximity effect 
C) covalent catalysis 
D) diffusion-controlled reaction 
E) acid-base catalysis

Question 7

Nucleophiles are often anions or have unshared electrons.

Accepted Answer

A) True 
 B)False

Question 8

How many intermediates are indicated by the energy diagram below?

Accepted Answer

A) One 
B) Two 
C) Three 
D) Four 
A) One 
B) Two 
C) Three 
D) Four

Question 9

A thermodynamic pit occurs when

Accepted Answer

A) ES is not very stable. 
B) ES forms faster than it dissociates. 
C) ES is highly stable. 
D) S is not bound tightly to an enzyme. 
E) S is positioned incorrectly to the enzyme. 
A) ES is not very stable. 
B) ES forms faster than it dissociates. 
C) ES is highly stable. 
D) S is not bound tightly to an enzyme. 
E) S is positioned incorrectly to the enzyme.

Question 10

Which statement does not apply to transition states?

Accepted Answer

A) Many have been detected experimentally. 
B) Chemical bonds are in the process of being formed and broken. 
C) Have lifetimes on the order of 10-14 to 10-13 seconds. 
D) Differ in energy from the ground state by the activation energy. 
A) Many have been detected experimentally. 
B) Chemical bonds are in the process of being formed and broken. 
C) Have lifetimes on the order of 10-14 to 10-13 seconds. 
D) Differ in energy from the ground state by the activation energy.

Question 11

Active trypsin formation by the action of enteropeptidase can be viewed as the master activation step because

Accepted Answer

A) enteropeptidase can activate its own zymogen. 
B) it is allosterically controlled. 
C) trypsin activates other pancreatic zymogens. 
D) All of the above. 
A) enteropeptidase can activate its own zymogen. 
B) it is allosterically controlled. 
C) trypsin activates other pancreatic zymogens. 
D) All of the above.

Question 12

Chemical modes of catalysis are more important than binding modes of catalysis in accounting for the accelerated rates of enzymatic reactions.

Accepted Answer

A) True 
 B)False

Question 13

Match each of these terms with the correct description:
-A substrate changes the shape of an enzyme and that activates it.

Accepted Answer

A) induced fit 
B) proximity effect 
C) covalent catalysis 
D) diffusion-controlled reaction 
E) acid-base catalysis 
A) induced fit 
B) proximity effect 
C) covalent catalysis 
D) diffusion-controlled reaction 
E) acid-base catalysis

Question 14

Match each of these terms with the correct description:
-There is a collision between reactant molecules.

Accepted Answer

A) induced fit 
B) proximity effect 
C) covalent catalysis 
D) diffusion-controlled reaction 
E) acid-base catalysis 
A) induced fit 
B) proximity effect 
C) covalent catalysis 
D) diffusion-controlled reaction 
E) acid-base catalysis

Question 15

The active site of a certain enzyme contains a serine residue.When the enzyme is incubated for a short time with its substrate,a form of the enzyme in which the active site serine is acetylated can be isolated and purified.In the native protein the serine is never found to be acetylated.This information supports ________.

Accepted Answer

A) a covalent catalysis mode 
B) intermediate state stabilization effects 
C) the acid-base catalysis mode 
D) a polar group catalytic mechanism 
A) a covalent catalysis mode 
B) intermediate state stabilization effects 
C) the acid-base catalysis mode 
D) a polar group catalytic mechanism

Question 16

In the modified "lock-and-key" theory of enzyme specificity,the key is still the enzyme while the lock is still the substrate.

Accepted Answer

A) True 
 B)False

Question 17

One reason the proximity effect enhances catalysis is because

Accepted Answer

A) the effective molarity of reactive substrate groups increases. 
B) the enzyme changes conformation to more readily accept the substrate as it approaches the active site. 
C) the active site becomes smaller. 
D) the catalytic triad in the active site becomes more flexible. 
A) the effective molarity of reactive substrate groups increases. 
B) the enzyme changes conformation to more readily accept the substrate as it approaches the active site. 
C) the active site becomes smaller. 
D) the catalytic triad in the active site becomes more flexible.

Question 18

In the nonpolar environment of most enzyme active sites,which statement applies to charge-charge interactions between the enzyme and the substrate?

Accepted Answer

A) They are rare due to the non-polar environment. 
B) They are frequent,but not very strong in the nonpolar environment. 
C) They are stronger in the nonpolar environment. 
D) The polarity of the active site has no effect on the strength of the charge-charge interactions. 
A) They are rare due to the non-polar environment. 
B) They are frequent,but not very strong in the nonpolar environment. 
C) They are stronger in the nonpolar environment. 
D) The polarity of the active site has no effect on the strength of the charge-charge interactions.

Question 19

On the energy diagram below,which arrow(s)represent the activation energy for the forward and reverse reactions?

Accepted Answer

A) Arrow 1 is the activation energy for both the forward and reverse reactions. 
B) Arrow 1 is the activation energy for the forward reaction and arrow 2 is the activation energy for the reverse reaction. 
C) Arrow 1 is the activation energy for the forward reaction and arrow 3 is the activation energy for the reverse reaction. 
D) Arrow 3 is the activation energy for the forward reaction and arrow 2 is the activation energy for the reverse reaction. 
A) Arrow 1 is the activation energy for both the forward and reverse reactions. 
B) Arrow 1 is the activation energy for the forward reaction and arrow 2 is the activation energy for the reverse reaction. 
C) Arrow 1 is the activation energy for the forward reaction and arrow 3 is the activation energy for the reverse reaction. 
D) Arrow 3 is the activation energy for the forward reaction and arrow 2 is the activation energy for the reverse reaction.

Question 20

Site directed mutagenesis is used to study enzymes by

Accepted Answer

A) changing the location of the active site. 
B) producing enzymes with different amino acid residues. 
C) producing enzymes with modified R groups. 
D) changing the pH of the environment. 
A) changing the location of the active site. 
B) producing enzymes with different amino acid residues. 
C) producing enzymes with modified R groups. 
D) changing the pH of the environment.

Exam 6: Mechanisms of Enzymes

Zymogens are often active only in the environment in which they are functional.

Transition state analogs should

Match each of these terms with the correct description: -Rely on amino acid side chains that can donate and accept protons at nearly neutral pH

An update of Fischer's lock-and-key theory of enzyme specificity views the ________ as the lock and ________ as the key.

A key role of the hydroxyl group at position 6 in the purine ring in the formation of a transition state by the enzyme adenosine deaminase is obtained by comparing a ________ and a ________.

Match each of these terms with the correct description: -Correct positioning of two reacting groups at the active site

Nucleophiles are often anions or have unshared electrons.

How many intermediates are indicated by the energy diagram below?

A thermodynamic pit occurs when

Which statement does not apply to transition states?

Active trypsin formation by the action of enteropeptidase can be viewed as the master activation step because

Chemical modes of catalysis are more important than binding modes of catalysis in accounting for the accelerated rates of enzymatic reactions.

Match each of these terms with the correct description: -A substrate changes the shape of an enzyme and that activates it.

Match each of these terms with the correct description: -There is a collision between reactant molecules.

In the modified "lock-and-key" theory of enzyme specificity,the key is still the enzyme while the lock is still the substrate.

One reason the proximity effect enhances catalysis is because

In the nonpolar environment of most enzyme active sites,which statement applies to charge-charge interactions between the enzyme and the substrate?

On the energy diagram below,which arrow(s)represent the activation energy for the forward and reverse reactions?

Site directed mutagenesis is used to study enzymes by

Introduction to Biochemistry

Water

Amino Acids and the Primary Structures of Proteins

Proteins: Three-Dimensional Structure and Function

Properties of Enzymes

Coenzymes and Vitamins

Carbohydrates

Lipids and Membranes

Introduction to Metabolism

Glycolysis

Gluconeogenesis, the Pentose Phosphate Pathway, and Glycogen Metabolism

The Citric Acid Cycle

Electron Transport and Atp Synthesis

Photosynthesis

Lipid Metabolism

Amino Acid Metabolism

Nucleotide Metabolism

Nucleic Acids

DNA Replication, repair, and Recombination

Transcription and RNA Processing

Protein Synthesis

Filters

An update of Fischer's lock-and-key theory of enzyme specificity views the as the lock and as the key.

A key role of the hydroxyl group at position 6 in the purine ring in the formation of a transition state by the enzyme adenosine deaminase is obtained by comparing a and a .