Question 1

Which of the following is implied by induced fit between the enzyme's active site and the substrate?

Accepted Answer

A)  The enzyme is a flexible molecule. 
B)  An enzyme will work equally well with different substrates. 
C)  An active site can bind to different substrates. 
D)  The enzyme is a flexible molecule so different substrates can bind. 
E)  All of these are correct 
A)  The enzyme is a flexible molecule. 
B)  An enzyme will work equally well with different substrates. 
C)  An active site can bind to different substrates. 
D)  The enzyme is a flexible molecule so different substrates can bind. 
E)  All of these are correct

Question 2

The rate of a zero-order reaction depends on the _____.

Accepted Answer

A)  total number of reactants 
B)  concentration of products 
C)  concentration of reactants 
D)  presence of catalysts 
A)  total number of reactants 
B)  concentration of products 
C)  concentration of reactants 
D)  presence of catalysts

Question 3

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 4

Nonenzymatic catalysts enhance the rate of a reaction by factors of _____.

Accepted Answer

A)  105 to 109 
B)  102 to 104 
C)  1015 to 1020 
D)  1022 to 1024 
A)  105 to 109 
B)  102 to 104 
C)  1015 to 1020 
D)  1022 to 1024

Question 5

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 6

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 7

Generally speaking, a competitive inhibitor and the substrate cannot both bind to the enzyme at the same time.

Accepted Answer

A) True 
 B)False

Question 8

Which of the following is not related to the others?

Accepted Answer

A)  Suicide Substrate 
B)  Irreversible Inhibitor 
C)  Trojan Horse substrate 
D)  Competitive Inhibitor 
E)  All of these are related 
A)  Suicide Substrate 
B)  Irreversible Inhibitor 
C)  Trojan Horse substrate 
D)  Competitive Inhibitor 
E)  All of these are related

Question 9

When the substrate concentration is low, an enzyme reaction

Accepted Answer

A)  will display zero-order kinetics. 
B)  will display first-order kinetics. 
C)  will display second-order kinetics. 
D)  will denature and cease to function. 
A)  will display zero-order kinetics. 
B)  will display first-order kinetics. 
C)  will display second-order kinetics. 
D)  will denature and cease to function.

Question 10

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 11

Which of the following is true about lactate dehydrogenase (LDH)?

Accepted Answer

A)  There are two types of subunits, H amd M, that combine to form 5 types of isozymes 
B)  An increase in H-based isozymes was once used to diagnose heart attacks 
C)  An increase in blood levels of LDH of any kind is indicative of some sort of problem 
D)  One type of LDH has only H subunits 
E)  All of the choices 
A)  There are two types of subunits, H amd M, that combine to form 5 types of isozymes 
B)  An increase in H-based isozymes was once used to diagnose heart attacks 
C)  An increase in blood levels of LDH of any kind is indicative of some sort of problem 
D)  One type of LDH has only H subunits 
E)  All of the choices

Question 12

Identify a true statement about the enzyme creatine kinase (CK).

Accepted Answer

A)  Creatine kinase (CK) is found only in brain and skeletal muscles. 
B)  After a heart attack, creatine kinase (CK) shows up more rapidly in blood than lactate dehydrogenase (LDH). 
C)  Creatine kinase (CK) is an isozyme as it can exist in five different forms. 
D)  A high level of creatine kinase (CK) in brain indicates normal functioning of the brain. 
A)  Creatine kinase (CK) is found only in brain and skeletal muscles. 
B)  After a heart attack, creatine kinase (CK) shows up more rapidly in blood than lactate dehydrogenase (LDH). 
C)  Creatine kinase (CK) is an isozyme as it can exist in five different forms. 
D)  A high level of creatine kinase (CK) in brain indicates normal functioning of the brain.

Question 13

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 KM of the enzyme?

Accepted Answer

A)  10 nM 
B)  0.1 µM 
C)  1 µM 
D)  10 µM 
A)  10 nM 
B)  0.1 µM 
C)  1 µM 
D)  10 µM

Question 14

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 15

Thermodynamically favorable reactions all release energy.

Accepted Answer

A) True 
 B)False

Question 16

When an enzyme-catalyzed reaction has two substrates and substrate A must bind before substrate B, the mechanism is called

Accepted Answer

A)  a ping-pong mechanism 
B)  a random mechanism 
C)  an ordered mechanism 
D)  a suicide mechanism 
E)  none of these is true 
A)  a ping-pong mechanism 
B)  a random mechanism 
C)  an ordered mechanism 
D)  a suicide mechanism 
E)  none of these is true

Question 17

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 Δ G. 
C)  Speed of a reaction is a kinetic parameter, not a thermodynamic one. 
D)  A reaction with a positive Δ G0 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 Δ G. 
C)  Speed of a reaction is a kinetic parameter, not a thermodynamic one. 
D)  A reaction with a positive Δ G0 can never happen

Question 18

Which of the following is true concerning a ping-pong mechanism?

Accepted Answer

A)  Either substrate can bind first 
B)  Either product can leave first 
C)  One product leaves before the second substrate binds 
D)  One product leaves before either substrate has bound 
E)  none of these are true 
A)  Either substrate can bind first 
B)  Either product can leave first 
C)  One product leaves before the second substrate binds 
D)  One product leaves before either substrate has bound 
E)  none of these are true

Question 19

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 20

The sign of Gibb's Free Energy is positive ("+") when energy is released.

Accepted Answer

A) True 
 B)False

Exam 6: The Behavior of Proteins Enzymes

Which of the following is implied by induced fit between the enzyme's active site and the substrate?

The rate of a zero-order reaction depends on the _____.

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

Nonenzymatic catalysts enhance the rate of a reaction by factors of _____.

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

As catalysts, enzymes are

Generally speaking, a competitive inhibitor and the substrate cannot both bind to the enzyme at the same time.

Which of the following is not related to the others?

When the substrate concentration is low, an enzyme reaction

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

Which of the following is true about lactate dehydrogenase (LDH)?

Identify a true statement about the enzyme creatine kinase (CK).

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

Thermodynamically favorable reactions all release energy.

When an enzyme-catalyzed reaction has two substrates and substrate A must bind before substrate B, the mechanism is called

Which of the following is not true?

Which of the following is true concerning a ping-pong mechanism?

For competitive inhibition

The sign of Gibb's Free Energy is positive ("+") when energy is released.

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

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