Question 1

Pure noncompetitive inhibition is a limiting case of

Accepted Answer

A)  Competitive inhibition 
B)  Uncompetitive inhibition 
C)  Irreversible inhibition 
D)  Mixed inhibition 
E)  None of these is true 
A)  Competitive inhibition 
B)  Uncompetitive inhibition 
C)  Irreversible inhibition 
D)  Mixed inhibition 
E)  None of these is true

Question 2

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 3

What effect is seen on a Lineweaver-Burk graph when a competitive inhibitor is added?

Accepted Answer

A)  The y-intercept is changed, but not change the slope of the line. 
B)  The slope of the line is changed, but not the y-intercept. 
C)  Both the y-intercept and the slope of the line are changed. 
D)  Neither the y-intercept not the slope of the line is changed. 
A)  The y-intercept is changed, but not change the slope of the line. 
B)  The slope of the line is changed, but not the y-intercept. 
C)  Both the y-intercept and the slope of the line are changed. 
D)  Neither the y-intercept not the slope of the line is changed.

Question 4

Most enzyme reactions display first order kinetics for the individual substrates when the substrate concentration is low.

Accepted Answer

A) True 
 B)False

Question 5

The kinetic order of a reaction

Accepted Answer

A)  can be determined by inspection from the coefficients of the balanced equation 
B)  must be determined experimentally 
C)  always depends on the concentration of enzyme 
D)  never depends on concentrations of reactants 
A)  can be determined by inspection from the coefficients of the balanced equation 
B)  must be determined experimentally 
C)  always depends on the concentration of enzyme 
D)  never depends on concentrations of reactants

Question 6

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 7

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 8

The KM of hexokinase for glucose = 0.15 mM and for fructose, KM = 1.5 mM. Which is the preferred substrate?

Accepted Answer

A)  Glucose. 
B)  Fructose. 
C)  Neither substrate is preferred over the other. 
D)  You cannot tell from the data given. 
E)  None of these answers is correct. 
A)  Glucose. 
B)  Fructose. 
C)  Neither substrate is preferred over the other. 
D)  You cannot tell from the data given. 
E)  None of these answers is correct.

Question 9

If an inhibitor changes the slope of the Lineweaver-Burk graph, but not the y-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 10

The steady state of an enzyme reaction is the following:

Accepted Answer

A)  The rate observed just after mixing the enzyme and substrate. 
B)  The rate observed and Vmax. 
C)  The rate of product formation. 
D)  The state which exists when E-S complex is forming as fast as it is breaking down. 
E)  The state which exists when substrate concentration equals KM. 
A)  The rate observed just after mixing the enzyme and substrate. 
B)  The rate observed and Vmax. 
C)  The rate of product formation. 
D)  The state which exists when E-S complex is forming as fast as it is breaking down. 
E)  The state which exists when substrate concentration equals KM.

Question 11

What effect is seen on a Lineweaver-Burk graph when a mixed-type inhibitor is added?

Accepted Answer

A)  The y-intercept is changed, but not change the slope of the line. 
B)  The slope of the line is changed, but not the y-intercept. 
C)  Both the y-intercept and the slope of the line are changed. 
D)  Neither the y-intercept not the slope of the line is changed. 
A)  The y-intercept is changed, but not change the slope of the line. 
B)  The slope of the line is changed, but not the y-intercept. 
C)  Both the y-intercept and the slope of the line are changed. 
D)  Neither the y-intercept not the slope of the line is changed.

Question 12

As catalysts, enzymes are

Accepted Answer

A)  significantly less effective than nonenzymatic catalysts 
B)  slightly less effective than nonenzymatic catalysts 
C)  significantly more effective than nonenzymatic catalysts 
D)  slightly more effective than nonenzymatic catalysts 
E)  exactly the same as nonenzymatic catalysts 
A)  significantly less effective than nonenzymatic catalysts 
B)  slightly less effective than nonenzymatic catalysts 
C)  significantly more effective than nonenzymatic catalysts 
D)  slightly more effective than nonenzymatic catalysts 
E)  exactly the same as nonenzymatic catalysts

Question 13

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 14

First order kinetics means:

Accepted Answer

A)  The rate of a reaction is independent of the amount of reactant measured. 
B)  The rate of the reaction varies directly with the amount of reactant measured. 
C)  The rate of the reaction varies with the square of the amount of the reactant measured. 
D)  More information is needed to answer this question. 
E)  None of these is correct. 
A)  The rate of a reaction is independent of the amount of reactant measured. 
B)  The rate of the reaction varies directly with the amount of reactant measured. 
C)  The rate of the reaction varies with the square of the amount of the reactant measured. 
D)  More information is needed to answer this question. 
E)  None of these is correct.

Question 15

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

Accepted Answer

A) True 
 B)False

Question 16

It is important that at physiological conditions, enzymes work at Vmax.

Accepted Answer

A) True 
 B)False

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

$k_{1}=10^{8} \mathrm{M}^{-1} \mathrm{~s}^{-1}, k_{-1}=100 \mathrm{~s}^{-1}, k_{2}=900 \mathrm{~s}^{-1}$
-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. 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 18

The Michaelis constant is

Accepted Answer

A)  related to the molecular weight of the enzyme 
B)  a measure of the resistance of the enzyme to denaturation 
C)  a reflection of the percentage of polar amino acids in the enzyme 
D)  a rough measure of the affinity of the enzyme for the substrate 
A)  related to the molecular weight of the enzyme 
B)  a measure of the resistance of the enzyme to denaturation 
C)  a reflection of the percentage of polar amino acids in the enzyme 
D)  a rough measure of the affinity of the enzyme for the substrate

Question 19

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 20

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

Exam 6: The Behavior of Proteins: Enzymes

Pure noncompetitive inhibition is a limiting case of

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

What effect is seen on a Lineweaver-Burk graph when a competitive inhibitor is added?

Most enzyme reactions display first order kinetics for the individual substrates when the substrate concentration is low.

The kinetic order of a reaction

Inhibitors can have the following effects on enzyme kinetics:

Which of the following is true about the enzyme chymotrypsin?

The KM of hexokinase for glucose = 0.15 mM and for fructose, KM = 1.5 mM. Which is the preferred substrate?

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

The steady state of an enzyme reaction is the following:

What effect is seen on a Lineweaver-Burk graph when a mixed-type inhibitor is added?

As catalysts, enzymes are

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

First order kinetics means:

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

It is important that at physiological conditions, enzymes work at Vmax.

The Michaelis constant is

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?

The rate of a reaction depends on

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 K_M of hexokinase for glucose = 0.15 mM and for fructose, K_M = 1.5 mM. Which is the preferred substrate?

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

It is important that at physiological conditions, enzymes work at V_max.