Question 1

The main difference between a catalyzed and an uncatalyzed reaction is that

Accepted Answer

A)  the activation energy of the catalyzed reaction is lower. 
B)  the catalyzed reaction has a more favorable free energy change. 
C)  the catalyzed reaction has a more favorable enthalpy change. 
D)  the catalyzed reaction has a more favorable entropy change. 
A)  the activation energy of the catalyzed reaction is lower. 
B)  the catalyzed reaction has a more favorable free energy change. 
C)  the catalyzed reaction has a more favorable enthalpy change. 
D)  the catalyzed reaction has a more favorable entropy change. A

Question 2

Exhibit 6A This is a reaction going on in your muscle cells right this very minute:   The enzyme triose phosphate isomerase catalyzes this reaction in the forward direction as part of the glycolytic pathway. It follows simple Michaelis-Menten kinetics:  
Typical cellular concentrations: triose phosphate isomerase = 0.1 nM
Dihydroxyacetone phosphate = 5 µM glyceraldehyde-3-phosphate = 2 µM
Refer to Exhibit 6A. "Hindrate" is an inhibitor of triose phosphate isomerase. When it is added to cells at a concentration of 0.1 nM, the enzyme's KM for the substrate is unchanged, but the apparent Vmax is altered to 50 nM\sec.
In the following graph, which line best represents the Lineweaver-Burk plot obtained in the presence of hindrate?

Accepted Answer

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

Question 3

Which of the following diseases has not been successfully treated using the principles of enzyme inhibition?

Accepted Answer

A)  AIDS. 
B)  Lactose intolerance 
C)  Virus infection 
D)  Neither AIDS nor virus infection. 
E)  All of these have been successfully treated using enzyme inhibitors. 
A)  AIDS. 
B)  Lactose intolerance 
C)  Virus infection 
D)  Neither AIDS nor virus infection. 
E)  All of these have been successfully treated using enzyme inhibitors. B

Question 4

In the induced-fit model of substrate binding to enzymes

Accepted Answer

A)  the substrate changes its conformation to fit the active site 
B)  the active site changes its conformation to fit the substrate 
C)  there is a conformational change in the enzyme when the substrate binds 
D)  there is aggregation of several enzyme molecules when the substrate binds 
A)  the substrate changes its conformation to fit the active site 
B)  the active site changes its conformation to fit the substrate 
C)  there is a conformational change in the enzyme when the substrate binds 
D)  there is aggregation of several enzyme molecules when the substrate binds

Question 5

Which of the following is true about the enzyme chymotrypsin?

Accepted Answer

A)  The enzyme can cleave peptides. 
B)  The enzyme can cleave esters. 
C)  The enzyme only binds to aromatic substrates. 
D)  The enzyme can cleave substrates which are not naturally occurring. 
E)  All of these are correct 
A)  The enzyme can cleave peptides. 
B)  The enzyme can cleave esters. 
C)  The enzyme only binds to aromatic substrates. 
D)  The enzyme can cleave substrates which are not naturally occurring. 
E)  All of these are correct

Question 6

To study the nature of an enzyme, Vmax is not as good a measurement as the catalytic rate constant kcat because:

Accepted Answer

A)  The Vmax is not a true constant since it depends on the concentration of enzyme 
B)  The Vmax cannot be measured 
C)  The Vmax is only valid for allosteric enzymes 
D)  none of these 
A)  The Vmax is not a true constant since it depends on the concentration of enzyme 
B)  The Vmax cannot be measured 
C)  The Vmax is only valid for allosteric enzymes 
D)  none of these

Question 7

The active site of an enzyme

Accepted Answer

A)  is frequently located in a cleft in the enzyme. 
B)  is the portion of the enzyme to which the substrate binds. 
C)  contains the reactive groups that catalyze the reaction. 
D)  all of these are correct 
A)  is frequently located in a cleft in the enzyme. 
B)  is the portion of the enzyme to which the substrate binds. 
C)  contains the reactive groups that catalyze the reaction. 
D)  all of these are correct

Question 8

Which of the following is true about a mixed type inhibition?

Accepted Answer

A)  A Lineweaver-Burk plot will give parallel lines 
B)  The KM will change but not the Vmax 
C)  The lines of a Lineweaver-Burk graph will cross in the top left quadrant 
D)  None of these is true 
A)  A Lineweaver-Burk plot will give parallel lines 
B)  The KM will change but not the Vmax 
C)  The lines of a Lineweaver-Burk graph will cross in the top left quadrant 
D)  None of these is true

Question 9

The E-S complex often shows as a slight depression in the energy profile for the reaction.

Accepted Answer

A) True 
 B)False

Question 10

A noncompetitive inhibitor

Accepted Answer

A)  binds to the enzyme at a site other than the active site 
B)  is structurally related to the substrate 
C)  does not affect the value of Vmax 
D)  decreases the value of KM 
A)  binds to the enzyme at a site other than the active site 
B)  is structurally related to the substrate 
C)  does not affect the value of Vmax 
D)  decreases the value of KM

Question 11

Non-competitive inhibitors have this effect:

Accepted Answer

A)  Modifying the KM value. 
B)  Changing the value for Vmax. 
C)  Interfering with substrate binding. 
D)  This type of inhibitor both changes the Vmax and interferes with substrate binding. 
E)  All of these are correct. 
A)  Modifying the KM value. 
B)  Changing the value for Vmax. 
C)  Interfering with substrate binding. 
D)  This type of inhibitor both changes the Vmax and interferes with substrate binding. 
E)  All of these are correct.

Question 12

The reaction catalyzed by aspartate transcarbamoylase is

Accepted Answer

A)  the first step in the synthesis of amino acids. 
B)  the first step in the synthesis of fatty acids. 
C)  the first step in the synthesis of CTP and UTP. 
D)  is part of glycolysis. 
A)  the first step in the synthesis of amino acids. 
B)  the first step in the synthesis of fatty acids. 
C)  the first step in the synthesis of CTP and UTP. 
D)  is part of glycolysis.

Question 13

Which of the following is true?

Accepted Answer

A)  The E-S complex often dissociates with no reaction taking place. 
B)  The E-S complex must form before a reaction can take place 
C)  Once the E-S complex forms, it can go on to form product or dissociate to E + S 
D)  All of these are correct 
A)  The E-S complex often dissociates with no reaction taking place. 
B)  The E-S complex must form before a reaction can take place 
C)  Once the E-S complex forms, it can go on to form product or dissociate to E + S 
D)  All of these are correct

Question 14

According to the steady-state assumption

Accepted Answer

A)  the product concentration does not change significantly 
B)  the substrate concentration is large and does not change significantly 
C)  the concentration of enzyme-substrate complex remains constant with time 
D)  the free enzyme concentration is always in great excess to the concentration of enzyme-substrate complex 
A)  the product concentration does not change significantly 
B)  the substrate concentration is large and does not change significantly 
C)  the concentration of enzyme-substrate complex remains constant with time 
D)  the free enzyme concentration is always in great excess to the concentration of enzyme-substrate complex

Question 15

Enzymatic activity has an optimum temperature because

Accepted Answer

A)  the component amino acids have varying melting points 
B)  the rate of reactions is thermodynamically controlled 
C)  the side chains of essential residues are chemically degraded at higher temperatures 
D)  raising the temperature speeds up the reaction until protein denaturation sets in 
E)  the organism dies beyond a certain temperature 
A)  the component amino acids have varying melting points 
B)  the rate of reactions is thermodynamically controlled 
C)  the side chains of essential residues are chemically degraded at higher temperatures 
D)  raising the temperature speeds up the reaction until protein denaturation sets in 
E)  the organism dies beyond a certain temperature

Question 16

Exhibit 6A This is a reaction going on in your muscle cells right this very minute:   The enzyme triose phosphate isomerase catalyzes this reaction in the forward direction as part of the glycolytic pathway. It follows simple Michaelis-Menten kinetics:  
Typical cellular concentrations: triose phosphate isomerase = 0.1 nM
Dihydroxyacetone phosphate = 5 µM glyceraldehyde-3-phosphate = 2 µM
Refer to Exhibit 6A. What is the equilibrium constant for the uncatalyzed reaction?

Accepted Answer

A)  0.9 
B)  1.1 
C)  2.5 
D)  Cannot be determined from the information provided. 
A)  0.9 
B)  1.1 
C)  2.5 
D)  Cannot be determined from the information provided.

Question 17

Exhibit 6A This is a reaction going on in your muscle cells right this very minute:   The enzyme triose phosphate isomerase catalyzes this reaction in the forward direction as part of the glycolytic pathway. It follows simple Michaelis-Menten kinetics:  
Typical cellular concentrations: triose phosphate isomerase = 0.1 nM
Dihydroxyacetone phosphate = 5 µM glyceraldehyde-3-phosphate = 2 µM
Refer to Exhibit 6A. "Hindrate" is an inhibitor of triose phosphate isomerase. When it is added to cells at a concentration of 0.1 nM, the enzyme's KM for the substrate is unchanged, but the apparent Vmax is altered to 50 nM\sec.

Accepted Answer

A)  This is a competitive inhibitor. 
B)  This is an uncompetitive inhibitor. 
C)  This is a noncompetitive inhibitor. 
D)  This is an irreversible inhibitor. 
A)  This is a competitive inhibitor. 
B)  This is an uncompetitive inhibitor. 
C)  This is a noncompetitive inhibitor. 
D)  This is an irreversible inhibitor.

Question 18

Exhibit 6A This is a reaction going on in your muscle cells right this very minute:   The enzyme triose phosphate isomerase catalyzes this reaction in the forward direction as part of the glycolytic pathway. It follows simple Michaelis-Menten kinetics:  
Typical cellular concentrations: triose phosphate isomerase = 0.1 nM
Dihydroxyacetone phosphate = 5 µM glyceraldehyde-3-phosphate = 2 µM
Refer to Exhibit 6A. What is the equilibrium constant for the enzyme-catalyzed reaction?

Accepted Answer

A)  0.9 
B)  1.1 
C)  2.5 
D)  Cannot be determined from the information provided. 
A)  0.9 
B)  1.1 
C)  2.5 
D)  Cannot be determined from the information provided.

Question 19

Exhibit 6A This is a reaction going on in your muscle cells right this very minute:   The enzyme triose phosphate isomerase catalyzes this reaction in the forward direction as part of the glycolytic pathway. It follows simple Michaelis-Menten kinetics:  
Typical cellular concentrations: triose phosphate isomerase = 0.1 nM
Dihydroxyacetone phosphate = 5 µM glyceraldehyde-3-phosphate = 2 µM
Refer to Exhibit 6A. What is the actual velocity of the forward reaction under physiologic conditions?

Accepted Answer

A)  2 nM\s 
B)  45 nM\s 
C)  500 nM\s 
D)  30 nM\s 
A)  2 nM\s 
B)  45 nM\s 
C)  500 nM\s 
D)  30 nM\s

Question 20

The amount of energy released during a reaction tells nothing about the rate at which that reaction will occur.

Accepted Answer

A) True 
 B)False

The main difference between a catalyzed and an uncatalyzed reaction is that

Which of the following diseases has not been successfully treated using the principles of enzyme inhibition?

In the induced-fit model of substrate binding to enzymes

Which of the following is true about the enzyme chymotrypsin?

To study the nature of an enzyme, V_max is not as good a measurement as the catalytic rate constant k_cat because:

The active site of an enzyme

Which of the following is true about a mixed type inhibition?

The E-S complex often shows as a slight depression in the energy profile for the reaction.

A noncompetitive inhibitor

Non-competitive inhibitors have this effect:

The reaction catalyzed by aspartate transcarbamoylase is

Which of the following is true?

According to the steady-state assumption

Enzymatic activity has an optimum temperature because

The amount of energy released during a reaction tells nothing about the rate at which that reaction will occur.

Biochemistry and the Organization of Cells

Water the Solvent for Biochemical Reactions

Amino Acids and Peptides

The Three Dimensional Structure of Proteins

Protein Purification and Characterization Techniques

The Behavior of Proteins Enzymes Mechanisms and Control

Lipids and Proteins Are Associated in Biological Membranes

Nucleic Acids How Structure Conveys Information

Biosynthesis of Nucleic Acids Replication

Transcription of the Genetic Code the Biosynthesis of Rna

Protein Synthesis Translation of the Genetic Message

Nucleic Acid Biotechnology Techniques

Viruses Cancer and Immunology

The Importance of Energy Changes and Electron Transfer in Metabolism

Carbohydrates

Glycolysis

Storage Mechanisms and Control in Carbohydrate Metabolism

The Citric Acid Cycle

Electron Transport and Oxidative Phosphorylation

Lipid Metabolism

Photosynthesis

The Metabolism of Nitrogen

Integration of Metabolism Cellular Signaling

Filters

Exam 6: The Behavior of Proteins Enzymes

The main difference between a catalyzed and an uncatalyzed reaction is that

Which of the following diseases has not been successfully treated using the principles of enzyme inhibition?

In the induced-fit model of substrate binding to enzymes

Which of the following is true about the enzyme chymotrypsin?

To study the nature of an enzyme, Vmax is not as good a measurement as the catalytic rate constant kcat because:

The active site of an enzyme

Which of the following is true about a mixed type inhibition?

The E-S complex often shows as a slight depression in the energy profile for the reaction.

A noncompetitive inhibitor

Non-competitive inhibitors have this effect:

The reaction catalyzed by aspartate transcarbamoylase is

Which of the following is true?

According to the steady-state assumption

Enzymatic activity has an optimum temperature because

The amount of energy released during a reaction tells nothing about the rate at which that reaction will occur.

Biochemistry and the Organization of Cells

Water the Solvent for Biochemical Reactions

Amino Acids and Peptides

The Three Dimensional Structure of Proteins

Protein Purification and Characterization Techniques

The Behavior of Proteins Enzymes Mechanisms and Control

Lipids and Proteins Are Associated in Biological Membranes

Nucleic Acids How Structure Conveys Information

Biosynthesis of Nucleic Acids Replication

Transcription of the Genetic Code the Biosynthesis of Rna

Protein Synthesis Translation of the Genetic Message

Nucleic Acid Biotechnology Techniques

Viruses Cancer and Immunology

The Importance of Energy Changes and Electron Transfer in Metabolism

Carbohydrates

Glycolysis

Storage Mechanisms and Control in Carbohydrate Metabolism

The Citric Acid Cycle

Electron Transport and Oxidative Phosphorylation

Lipid Metabolism

Photosynthesis

The Metabolism of Nitrogen

Integration of Metabolism Cellular Signaling

Filters

To study the nature of an enzyme, V_max is not as good a measurement as the catalytic rate constant k_cat because: