Question 1

Irreversible inhibitors of enzymatic reactions

Accepted Answer

A)  bind to the enzyme only at low temperatures. 
B)  affect only serine side chains. 
C)  react with the enzyme to produce a protein that is not enzymatically active and from which the original enzyme cannot be regenerated. 
D)  are bound to the enzyme by the lock-and-key mechanism. 
A)  bind to the enzyme only at low temperatures. 
B)  affect only serine side chains. 
C)  react with the enzyme to produce a protein that is not enzymatically active and from which the original enzyme cannot be regenerated. 
D)  are bound to the enzyme by the lock-and-key mechanism.

Question 2

The Michaelis-Menten approach to describing the kinetics of an enzyme-catalyzed reaction makes which of the following assumptions about the conversion of product into substrate?

Accepted Answer

A)  The product binds reversibly to the enzyme in order to be converted into the substrate. 
B)  The product is not converted to substrate to any appreciable extent. 
C)  The product is converted to substrate following simple first order kinetics. 
D)  The product is converted to substrate following simple second order kinetics. 
A)  The product binds reversibly to the enzyme in order to be converted into the substrate. 
B)  The product is not converted to substrate to any appreciable extent. 
C)  The product is converted to substrate following simple first order kinetics. 
D)  The product is converted to substrate following simple second order kinetics.

Question 3

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 4

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. "Restrainin" is an inhibitor of triose phosphate isomerase. When it is added to cells at a concentration of 0.4 nM, the enzyme's apparent KM for the substrate is altered to 100 µM, but the Vmax is unchanged.

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 5

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 6

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. "Restrainin" is an inhibitor of triose phosphate isomerase. When it is added to cells at a concentration of 0.4 nM, the enzyme's apparent KM for the substrate is altered to 100 µM, but the Vmax is unchanged.
In the following graph, which line best represents the Lineweaver-Burk plot obtained in the presence of restrainin?

Accepted Answer

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

Question 7

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 8

​ Explain the mechanism of the lock-and-key model of enzyme-substrate binding.

Accepted Answer

The lock-and-key model assumes a high de

Question 9

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

Question 10

The rate of the reaction of glycogen n with inorganic phosphate, P i , to form glucose-1-phosphate and glycogen n -1 is _____.

Accepted Answer

A)  rate = k [Glycogen]1[P i ]1 
B)  rate = k [Glycogen]0[P i ]1 
C)  rate = k [Glucose-1-phosphate]1[P i ]1 
D)  rate = k [Glucose-1-phosphate]0[P i ]1 
A)  rate = k [Glycogen]1[P i ]1 
B)  rate = k [Glycogen]0[P i ]1 
C)  rate = k [Glucose-1-phosphate]1[P i ]1 
D)  rate = k [Glucose-1-phosphate]0[P i ]1

Question 11

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 12

The rate of a reaction depends on

Accepted Answer

A)  the free energy change 
B)  the activation energy 
C)  the enthalpy change 
D)  the entropy change 
A)  the free energy change 
B)  the activation energy 
C)  the enthalpy change 
D)  the entropy change

Question 13

The drug acetazolamide:

Accepted Answer

A)  Is used to help fight altitude sickness 
B)  Was found to ruin the taste of carbonated beverages 
C)  Does not affect the taste of non-carbonated liquors 
D)  Causes its effect on taste by inhibiting carbonic anhydrase 4 
E)  All of these 
A)  Is used to help fight altitude sickness 
B)  Was found to ruin the taste of carbonated beverages 
C)  Does not affect the taste of non-carbonated liquors 
D)  Causes its effect on taste by inhibiting carbonic anhydrase 4 
E)  All of these

Question 14

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 15

The Michaelis constant determines the Vmax of an enzymatic reaction.

Accepted Answer

A) True 
 B)False

Question 16

The fundamental difference between competitive and noncompetitive inhibition is

Accepted Answer

A)  the degree of cooperativity of the reaction 
B)  the size of the active site of the enzyme 
C)  the manner of binding of substrate to the enzyme 
D)  the manner of binding of inhibitor to the enzyme 
A)  the degree of cooperativity of the reaction 
B)  the size of the active site of the enzyme 
C)  the manner of binding of substrate to the enzyme 
D)  the manner of binding of inhibitor to the enzyme

Question 17

Which of the following is most directly related to the speed of a reaction?

Accepted Answer

A)  The temperature 
B)  The Δ G0 of the reaction 
C)  The Δ G of the reaction 
D)  The Δ G0‡ of the reaction 
E)  None of these is correct. 
A)  The temperature 
B)  The Δ G0 of the reaction 
C)  The Δ G of the reaction 
D)  The Δ G0‡ of the reaction 
E)  None of these is correct.

Question 18

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 19

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 20

The substrate will only bind to the enzyme when the shapes fit together rigidly.

Accepted Answer

A) True 
 B)False

Exam 6: The Behavior of Proteins Enzymes

Irreversible inhibitors of enzymatic reactions

The Michaelis-Menten approach to describing the kinetics of an enzyme-catalyzed reaction makes which of the following assumptions about the conversion of product into substrate?

Inhibitors can have the following effects on enzyme kinetics:

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

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

​ Explain the mechanism of the lock-and-key model of enzyme-substrate binding.

The value of Vmax changes in

The rate of the reaction of glycogen n with inorganic phosphate, P i , to form glucose-1-phosphate and glycogen n -1 is _____.

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

The rate of a reaction depends on

The drug acetazolamide:

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

The Michaelis constant determines the Vmax of an enzymatic reaction.

The fundamental difference between competitive and noncompetitive inhibition is

Which of the following is most directly related to the speed of a reaction?

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

The KM expression is equal to

The substrate will only bind to the enzyme when the shapes fit together rigidly.

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

Explain the mechanism of the lock-and-key model of enzyme-substrate binding.

The value of V_max changes in

The rate of the reaction of glycogen _n with inorganic phosphate, P _i , to form glucose-1-phosphate and glycogen _n _-1 is _____.

The Michaelis constant determines the V_max of an enzymatic reaction.

The K_M expression is equal to