Question 1

Zymogens are

Accepted Answer

A)  inactive precursors of enzymes which can be activated by the irreversible cleavage of covalent bonds. 
B)  inactive forms of enzymes which require phosphorylation by a kinase to become active. 
C)  allosteric enzymes that are always in the R state. 
D)  allosteric enzymes that are always in the T state. 
A)  inactive precursors of enzymes which can be activated by the irreversible cleavage of covalent bonds. 
B)  inactive forms of enzymes which require phosphorylation by a kinase to become active. 
C)  allosteric enzymes that are always in the R state. 
D)  allosteric enzymes that are always in the T state. A

Question 2

Cofactors are

Accepted Answer

A)  non-protein in chemical nature. 
B)  always small proteins. 
C)  modified amino acids. 
D)  never required for enzymatic activity. 
A)  non-protein in chemical nature. 
B)  always small proteins. 
C)  modified amino acids. 
D)  never required for enzymatic activity. A

Question 3

The saturation curve for aspartyl transcarbamylase has a similar shape to the curve for:

Accepted Answer

A)  Myoglobin 
B)  Hemoglobin 
C)  Chymotrypsin 
D)  Both hemoglobin and chymotrypsin. 
E)  All of these. 
A)  Myoglobin 
B)  Hemoglobin 
C)  Chymotrypsin 
D)  Both hemoglobin and chymotrypsin. 
E)  All of these. B

Question 4

B vitamins are often stored in the body.

Accepted Answer

A) True 
 B)False

Question 5

Phosphorylation and allosteric control of enzymes.

Accepted Answer

A)  are not involved in reactions of carbohydrates. 
B)  play an insignificant role in generating energy. 
C)  are important processes in prokaryotes, but not in eukaryotes. 
D)  can be combined to afford a high degree of control over enzymatic reactions. 
E)  none of these 
A)  are not involved in reactions of carbohydrates. 
B)  play an insignificant role in generating energy. 
C)  are important processes in prokaryotes, but not in eukaryotes. 
D)  can be combined to afford a high degree of control over enzymatic reactions. 
E)  none of these

Question 6

Acyl transfer reactions often use this cofactor:

Accepted Answer

A)  Riboflavin 
B)  Lipoic acid 
C)  Pyridoxal 
D)  Thiamine 
E)  Biotin 
A)  Riboflavin 
B)  Lipoic acid 
C)  Pyridoxal 
D)  Thiamine 
E)  Biotin

Question 7

Which of the following is true about caspases?

Accepted Answer

A)  they are a class of proteases 
B)  they are involved in apoptosis 
C)  they are initially produced as inactive procaspases 
D)  once activated, they attach specific targets leading to cell death 
E)  all of these 
A)  they are a class of proteases 
B)  they are involved in apoptosis 
C)  they are initially produced as inactive procaspases 
D)  once activated, they attach specific targets leading to cell death 
E)  all of these

Question 8

Which of the following is not a difference between the concerted model and the sequential model of allosteric enzymes?

Accepted Answer

A)  The sequential model allows for different subunits to be in different conformations while the concerted model does not 
B)  Negative cooperativity can be explained by the sequential model but not by the concerted model 
C)  Positive cooperativity can be explained by the sequential model but not by the concerted model 
D)  The sequential model is explained better by considering the induced-fit model of substrate binding, whereas the concerted model focuses on perturbing the equilibrium between the T and R forms. 
A)  The sequential model allows for different subunits to be in different conformations while the concerted model does not 
B)  Negative cooperativity can be explained by the sequential model but not by the concerted model 
C)  Positive cooperativity can be explained by the sequential model but not by the concerted model 
D)  The sequential model is explained better by considering the induced-fit model of substrate binding, whereas the concerted model focuses on perturbing the equilibrium between the T and R forms.

Question 9

Abzymes

Accepted Answer

A)  invariably bind to pyridoxal phosphate. 
B)  are antibodies with catalytic activity. 
C)  differ markedly from transition states in enzymatic reactions. 
D)  have proline as part of their structure. 
A)  invariably bind to pyridoxal phosphate. 
B)  are antibodies with catalytic activity. 
C)  differ markedly from transition states in enzymatic reactions. 
D)  have proline as part of their structure.

Question 10

Which of the following is an advantage of an allosteric drug compared to an orthosteric one?

Accepted Answer

A)  they can modulate their effect in a more subtle way 
B)  an allosteric drug may be more specific for a specific reaction than one that binds to the receptor itself 
C)  they may be safer as they have no effect at all unless the natural substrate is present 
D)  all of these are advantages 
E)  none of these is an advantage 
A)  they can modulate their effect in a more subtle way 
B)  an allosteric drug may be more specific for a specific reaction than one that binds to the receptor itself 
C)  they may be safer as they have no effect at all unless the natural substrate is present 
D)  all of these are advantages 
E)  none of these is an advantage

Question 11

Pyridoxal phosphate is required for transfer of

Accepted Answer

A)  one-carbon groups 
B)  amino groups 
C)  acyl groups 
D)  aldehyde groups 
A)  one-carbon groups 
B)  amino groups 
C)  acyl groups 
D)  aldehyde groups

Question 12

The critical serine residue in the active site of chymotrypsin functions as

Accepted Answer

A)  a nucleophile. 
B)  an electrophile. 
C)  a base. 
D)  a methyl donor. 
E)  none of these 
A)  a nucleophile. 
B)  an electrophile. 
C)  a base. 
D)  a methyl donor. 
E)  none of these

Question 13

Which of the following is NOT required in order for an enzyme to display cooperative kinetics?

Accepted Answer

A)  Multiple subunits. 
B)  A value for the Michaelis constant, KM. 
C)  Allosteric sites which affect the binding of substrate to the active site. 
D)  Ability to display a Vmax. 
E)  All of these are characteristic of cooperative enzymes. 
A)  Multiple subunits. 
B)  A value for the Michaelis constant, KM. 
C)  Allosteric sites which affect the binding of substrate to the active site. 
D)  Ability to display a Vmax. 
E)  All of these are characteristic of cooperative enzymes.

Question 14

The concerted model for allosteric behavior was proposed by:

Accepted Answer

A)  Koshland 
B)  Pauling 
C)  Pasteur 
D)  Monod, Wyman and Changeux 
E)  All of these 
A)  Koshland 
B)  Pauling 
C)  Pasteur 
D)  Monod, Wyman and Changeux 
E)  All of these

Question 15

Which of the following is true?

Accepted Answer

A)  Phosphorylation always increases enzyme activity 
B)  Kinases often use AMP as a co-substrate in their phosphorylation reactions 
C)  Some enzymes are activated by phosphorylation while others are inhibited 
D)  ADP is the most common substrate for a kinase reaction 
A)  Phosphorylation always increases enzyme activity 
B)  Kinases often use AMP as a co-substrate in their phosphorylation reactions 
C)  Some enzymes are activated by phosphorylation while others are inhibited 
D)  ADP is the most common substrate for a kinase reaction

Question 16

How do each of these compounds affect the function of ATCase?

Accepted Answer

A)  ATP inhibits and CTP activates 
B)  ATP activates and CTP inhibits 
C)  Both ATP and CTP inhibit 
D)  Both ATP and CTP activate 
E)  none of these is true 
A)  ATP inhibits and CTP activates 
B)  ATP activates and CTP inhibits 
C)  Both ATP and CTP inhibit 
D)  Both ATP and CTP activate 
E)  none of these is true

Question 17

In the concerted model for allosteric enzymes, if the taut form of the enzyme cannot bind substrate then

Accepted Answer

A)  KT R 
B)  L = R/T 
C)  c = 0 
D)  an inhibitor must be present 
E)  none of these 
A)  KT R 
B)  L = R/T 
C)  c = 0 
D)  an inhibitor must be present 
E)  none of these

Question 18

Allosteric enzymes must exhibit which of the following?

Accepted Answer

A)  feedback inhibition 
B)  a phosphorylation site 
C)  general acid-base catalysis 
D)  a quaternary structure 
E)  none of these must be exhibited 
A)  feedback inhibition 
B)  a phosphorylation site 
C)  general acid-base catalysis 
D)  a quaternary structure 
E)  none of these must be exhibited

Question 19

Which of the following amino acid side chains would best serve as a general acid, assuming the protein functions at a pH of 7?

Accepted Answer

A)  alanine 
B)  aspartic acid 
C)  lysine 
D)  asparagine 
A)  alanine 
B)  aspartic acid 
C)  lysine 
D)  asparagine

Question 20

Generally speaking, enzymes involved in pathways which generate ATP will be activated by addition of phosphate groups to the enzyme.

Accepted Answer

A) True 
 B)False

Exam 7: The Behavior of Proteins: Enzymes, Mechanisms, and Control

Zymogens are

Cofactors are

The saturation curve for aspartyl transcarbamylase has a similar shape to the curve for:

B vitamins are often stored in the body.

Phosphorylation and allosteric control of enzymes.

Acyl transfer reactions often use this cofactor:

Which of the following is true about caspases?

Which of the following is not a difference between the concerted model and the sequential model of allosteric enzymes?

Abzymes

Which of the following is an advantage of an allosteric drug compared to an orthosteric one?

Pyridoxal phosphate is required for transfer of

The critical serine residue in the active site of chymotrypsin functions as

Which of the following is NOT required in order for an enzyme to display cooperative kinetics?

The concerted model for allosteric behavior was proposed by:

Which of the following is true?

How do each of these compounds affect the function of ATCase?

In the concerted model for allosteric enzymes, if the taut form of the enzyme cannot bind substrate then

Allosteric enzymes must exhibit which of the following?

Which of the following amino acid side chains would best serve as a general acid, assuming the protein functions at a pH of 7?

Generally speaking, enzymes involved in pathways which generate ATP will be activated by addition of phosphate groups to the enzyme.

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

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

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