Question 1

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 2

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.

Question 3

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 ΔG. 
C)  Speed of a reaction is a kinetic parameter, not a thermodynamic one. 
D)  A reaction with a positive ΔG0 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 ΔG. 
C)  Speed of a reaction is a kinetic parameter, not a thermodynamic one. 
D)  A reaction with a positive ΔG0 can never happen

Question 4

The Michaelis constant determines the Vmax of an enzymatic reaction.

Accepted Answer

A) True 
 B)False

Question 5

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 6

If an inhibitor changes the slope of the Lineweaver-Burk graph, but not the x-intercept, it is this type of inhibition:

Accepted Answer

A)  Competitive. 
B)  Non-competitive. 
C)  Mixed Inhibition (uncompetitive inhibition). 
D)  You cannot tell from the data given. 
E)  More than one answer is correct. 
A)  Competitive. 
B)  Non-competitive. 
C)  Mixed Inhibition (uncompetitive inhibition). 
D)  You cannot tell from the data given. 
E)  More than one answer is correct.

Question 7

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.

Question 8

Which of the following is the most unique about an uncompetitive inhibitor?

Accepted Answer

A)  It affects the KM of the enzyme 
B)  It affects the Vmax of the enzyme 
C)  It can be identified by a Lineweaver-Burk plot 
D)  The inhibitor can bind to ES but not to free E 
E)  None of these is particularly unique to an uncompetitive inhibitor 
A)  It affects the KM of the enzyme 
B)  It affects the Vmax of the enzyme 
C)  It can be identified by a Lineweaver-Burk plot 
D)  The inhibitor can bind to ES but not to free E 
E)  None of these is particularly unique to an uncompetitive inhibitor

Question 9

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

Accepted Answer

A)  The temperature 
B)  The ΔG0 of the reaction 
C)  The ΔG of the reaction 
D)  The ΔG0‡ of the reaction 
E)  None of these is correct. 
A)  The temperature 
B)  The ΔG0 of the reaction 
C)  The ΔG of the reaction 
D)  The ΔG0‡ of the reaction 
E)  None of these is correct.

Question 10

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

$k_{1}=10^{8} \mathrm{M}^{-1} \mathrm{~s}^{-1}, k_{-1}=100 \mathrm{~s}^{-1}, k_{2}=900 \mathrm{~s}^{-1}$
-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 11

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 12

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 13

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

Accepted Answer

A)  0.0254 millimolar (mM). 
B)  0.523 millimolar (mM). 
C)  5.23 millimolar (mM). 
D)  39.4 millimolar (mM). 
E)  75.3 millimolar (mM). 
A)  0.0254 millimolar (mM). 
B)  0.523 millimolar (mM). 
C)  5.23 millimolar (mM). 
D)  39.4 millimolar (mM). 
E)  75.3 millimolar (mM).

Question 14

For competitive inhibition

Accepted Answer

A)  the value of KM decreases 
B)  the value of Vmax decreases 
C)  it is possible to overcome the effect of the inhibitor by increasing the concentration of substrate 
D)  none of the above 
A)  the value of KM decreases 
B)  the value of Vmax decreases 
C)  it is possible to overcome the effect of the inhibitor by increasing the concentration of substrate 
D)  none of the above

Question 15

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 16

All catalysts work by lowering the activation energy for a reaction.

Accepted Answer

A) True 
 B)False

Question 17

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 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

$k_{1}=10^{8} \mathrm{M}^{-1} \mathrm{~s}^{-1}, k_{-1}=100 \mathrm{~s}^{-1}, k_{2}=900 \mathrm{~s}^{-1}$
-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 19

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 20

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.

Exam 6: The Behavior of Proteins: Enzymes

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

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

Which of the following is not true?

The Michaelis constant determines the Vmax of an enzymatic reaction.

The value of Vmax changes in

If an inhibitor changes the slope of the Lineweaver-Burk graph, but not the x-intercept, it is this type of inhibition:

A rate constant is

Which of the following is the most unique about an uncompetitive inhibitor?

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

A noncompetitive inhibitor

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

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

For competitive inhibition

According to the steady-state assumption

All catalysts work by lowering the activation energy for a reaction.

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

The active site of an enzyme

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

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 Michaelis constant determines the V_max of an enzymatic reaction.

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, K_M equals: