Question 1

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 
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 D

Question 2

A rate constant is

Accepted Answer

A)  the rate of a reaction at standard temperature and pressure. 
B)  the rate of a reaction at equilibrium. 
C)  a proportionality constant relating the rate of a reaction to the concentration(s) of the reactant(s). 
D)  a kind of transition state. 
A)  the rate of a reaction at standard temperature and pressure. 
B)  the rate of a reaction at equilibrium. 
C)  a proportionality constant relating the rate of a reaction to the concentration(s) of the reactant(s). 
D)  a kind of transition state. C

Question 3

The value of Vmax changes in

Accepted Answer

A)  competitive inhibition 
B)  noncompetitive inhibition 
C)  both forms of inhibition 
D)  neither form of inhibition 
A)  competitive inhibition 
B)  noncompetitive inhibition 
C)  both forms of inhibition 
D)  neither form of inhibition B

Question 4

The rate of a reaction is always dependent on the concentration(s) of the reactant(s).

Accepted Answer

A) True 
 B)False

Question 5

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 
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

Question 6

A Lineweaver-Burk plot is useful in the analysis of enzymatic reactions because

Accepted Answer

A)  it is easier to see whether points deviate from a straight line than from a curve 
B)  it is not affected by the presence of inhibitors 
C)  it can be used whether or not the enzyme displays Michaelis-Menten kinetics 
D)  all of the above 
A)  it is easier to see whether points deviate from a straight line than from a curve 
B)  it is not affected by the presence of inhibitors 
C)  it can be used whether or not the enzyme displays Michaelis-Menten kinetics 
D)  all of the above

Question 7

Which of the following is more likely to inhibit regulatory subunits of an allosteric enzyme?

Accepted Answer

A)  A competitive inhibitor 
B)  A non-competitive inhibitor 
C)  An irreversible inhibitor 
D)  All of these are equally likely to inhibit a regulatory subunit 
A)  A competitive inhibitor 
B)  A non-competitive inhibitor 
C)  An irreversible inhibitor 
D)  All of these are equally likely to inhibit a regulatory subunit

Question 8

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 
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

Question 9

Which of the following inhibitors binds to the enzyme at a site other than the active site?

Accepted Answer

A)  competitive inhibitor 
B)  noncompetitive inhibitor 
C)  irreversible inhibitor 
D)  all of these 
E)  none of these 
A)  competitive inhibitor 
B)  noncompetitive inhibitor 
C)  irreversible inhibitor 
D)  all of these 
E)  none of these

Question 10

Inhibitors can have the following effects on enzyme kinetics:

Accepted Answer

A)  Modifying the KM value. 
B)  Changing the value for Vmax. 
C)  Interfering with substrate binding. 
D)  An inhibitor can change the KM and interfere 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)  An inhibitor can change the KM and interfere with substrate binding. 
E)  All of these are correct.

Question 11

If the y-intercept of a Lineweaver-Burk plot = 1.91 (sec/millimole) and the slope = 75.3 L/sec,Vmax equals:

Accepted Answer

A)  0.0254 millimoles per second. 
B)  0.523 millimoles per second. 
C)  5.23 millimoles per second. 
D)  39.4 millimoles per second. 
E)  75.3 millimoles per second. 
A)  0.0254 millimoles per second. 
B)  0.523 millimoles per second. 
C)  5.23 millimoles per second. 
D)  39.4 millimoles per second. 
E)  75.3 millimoles per second.

Question 12

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 13

In the reaction catalyzed by chymotrypsin,a graph in which the rate is plotted against the concentration of substrate

Accepted Answer

A)  is sigmoidal, characteristic of an allosteric enzyme 
B)  shows that cooperative kinetics are observed 
C)  shows that the reaction is zero order 
D)  is hyperbolic, characteristic of a nonallosteric enzyme 
A)  is sigmoidal, characteristic of an allosteric enzyme 
B)  shows that cooperative kinetics are observed 
C)  shows that the reaction is zero order 
D)  is hyperbolic, characteristic of a nonallosteric enzyme

Question 14

Which of the following statements regarding the Michaelis constant is false?

Accepted Answer

A)  It is similar to the affinity constant between the enzyme and substrate. 
B)  The dimension for the Michaelis constant is concentration, such as molarity. 
C)  The Michaelis constant determines the Vmax. 
D)  It is the substrate concentration necessary to reach 1/2 Vmax. 
A)  It is similar to the affinity constant between the enzyme and substrate. 
B)  The dimension for the Michaelis constant is concentration, such as molarity. 
C)  The Michaelis constant determines the Vmax. 
D)  It is the substrate concentration necessary to reach 1/2 Vmax.

Question 15

Which of the following is not true?

Accepted Answer

A)  In thermodynamics, spontaneous does not mean instantaneous or even fast. 
B)  If a reaction is spontaneous then it has a negative DG. 
C)  Speed of a reaction is a kinetic parameter, not a thermodynamic one. 
D)  A reaction with a positive DG0 can never happen 
A)  In thermodynamics, spontaneous does not mean instantaneous or even fast. 
B)  If a reaction is spontaneous then it has a negative DG. 
C)  Speed of a reaction is a kinetic parameter, not a thermodynamic one. 
D)  A reaction with a positive DG0 can never happen

Question 16

How much faster is a reaction with the fastest enzyme than without a catalyst?

Accepted Answer

A)  About 10 times faster. 
B)  About 100 times faster. 
C)  About 1,000 times faster. 
D)  About 10,000 times faster. 
E)  About 1020 times faster. 
A)  About 10 times faster. 
B)  About 100 times faster. 
C)  About 1,000 times faster. 
D)  About 10,000 times faster. 
E)  About 1020 times faster.

Question 17

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

Question 18

The KM expression is equal to

Accepted Answer

A)  (k1 + k2) / k-1 
B)  (k-1 + k2) / k1 
C)  (k1 + k-1) / k2 
D)  k-1 / k1 
A)  (k1 + k2) / k-1 
B)  (k-1 + k2) / k1 
C)  (k1 + k-1) / k2 
D)  k-1 / k1

Question 19

The active site of an enzyme is the place where the following happens:

Accepted Answer

A)  The enzyme substrate complex forms here. 
B)  The catalytic reaction happens here. 
C)  Allosteric regulation of enzyme rate occurs here. 
D)  The enzyme-substrate complex forms and the reaction occurs at the active site. 
E)  All of these are correct. 
A)  The enzyme substrate complex forms here. 
B)  The catalytic reaction happens here. 
C)  Allosteric regulation of enzyme rate occurs here. 
D)  The enzyme-substrate complex forms and the reaction occurs at the active site. 
E)  All of these are correct.

Question 20

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

Exam 6: The Behavior of Proteins: Enzymes

Enzymatic activity has an optimum temperature because

A rate constant is

The value of Vmax changes in

The rate of a reaction is always dependent on the concentration(s) of the reactant(s).

Which of the following is true?

A Lineweaver-Burk plot is useful in the analysis of enzymatic reactions because

Which of the following is more likely to inhibit regulatory subunits of an allosteric enzyme?

The active site of an enzyme

Which of the following inhibitors binds to the enzyme at a site other than the active site?

Inhibitors can have the following effects on enzyme kinetics:

If the y-intercept of a Lineweaver-Burk plot = 1.91 (sec/millimole) and the slope = 75.3 L/sec,Vmax equals:

In the reaction catalyzed by chymotrypsin,a graph in which the rate is plotted against the concentration of substrate

Which of the following statements regarding the Michaelis constant is false?

Which of the following is not true?

How much faster is a reaction with the fastest enzyme than without a catalyst?

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

The KM expression is equal to

The active site of an enzyme is the place where the following happens:

In the induced-fit model of substrate binding to enzymes

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: 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

The value of V_max changes in

If the y-intercept of a Lineweaver-Burk plot = 1.91 (sec/millimole) and the slope = 75.3 L/sec,V_max equals:

The K_M expression is equal to