Question 1

An important step in elucidating the behavior of an enzyme is

Accepted Answer

A)  obtaining a crystalline sample of the enzyme. 
B)  insuring that metal ions are always excluded from the enzyme sample. 
C)  determining the active site residues. 
D)  none of these 
A)  obtaining a crystalline sample of the enzyme. 
B)  insuring that metal ions are always excluded from the enzyme sample. 
C)  determining the active site residues. 
D)  none of these

Question 2

Nicotinamide adenine dinucleotide is

Accepted Answer

A)  an enzyme inhibitor used in smoking cessation programs. 
B)  an inhibitor of ATP production. 
C)  a coenzyme in reactions that transfer acyl groups. 
D)  a coenzyme in oxidation-reduction reactions. 
A)  an enzyme inhibitor used in smoking cessation programs. 
B)  an inhibitor of ATP production. 
C)  a coenzyme in reactions that transfer acyl groups. 
D)  a coenzyme in oxidation-reduction reactions.

Question 3

Which of the following is not true about B vitamins?

Accepted Answer

A)  They are usually fully active in the form we eat them 
B)  They are usually water soluble 
C)  Niacin and riboflavin are examples 
D)  They are important in many metabolic reactions 
A)  They are usually fully active in the form we eat them 
B)  They are usually water soluble 
C)  Niacin and riboflavin are examples 
D)  They are important in many metabolic reactions

Question 4

In reactions catalyzed by allosteric enzymes

Accepted Answer

A)  substrate, activators, and inhibitors all compete for the same binding site on the enzyme. 
B)  there is no distinction between catalytic and regulatory subunits. 
C)  the presence of an activator makes the plot of reaction rate against substrate concentration less cooperative. 
D)  the presence of an inhibitor makes the plot of reaction rate against substrate concentration less cooperative. 
A)  substrate, activators, and inhibitors all compete for the same binding site on the enzyme. 
B)  there is no distinction between catalytic and regulatory subunits. 
C)  the presence of an activator makes the plot of reaction rate against substrate concentration less cooperative. 
D)  the presence of an inhibitor makes the plot of reaction rate against substrate concentration less cooperative.

Question 5

The concerted and sequential models for the behavior of allosteric enzymes differ in

Accepted Answer

A)  the conformational change in the enzyme in one model and not in the other. 
B)  the number of predicted binding sites on the enzyme. 
C)  the manner in which changes in quaternary structure take place. 
D)  the response of the enzyme to changes in temperature. 
A)  the conformational change in the enzyme in one model and not in the other. 
B)  the number of predicted binding sites on the enzyme. 
C)  the manner in which changes in quaternary structure take place. 
D)  the response of the enzyme to changes in temperature.

Question 6

In a comparison of allosteric and non-allosteric enzymes

Accepted Answer

A)  it is always possible to define a KM 
B)  it is always possible to define a Vmax 
C)  competitive inhibition is always a possibility 
D)  much of the terminology is completely unchanged 
A)  it is always possible to define a KM 
B)  it is always possible to define a Vmax 
C)  competitive inhibition is always a possibility 
D)  much of the terminology is completely unchanged

Question 7

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

Question 8

What happens when a K-acting inhibitor is added to an allosteric enzyme system?

Accepted Answer

A)  The apparent KM for the substrate increases. 
B)  The apparent KM for the substrate decreases. 
C)  The apparent Vmax for the substrate increases. 
D)  The apparent Vmax for the substrate decreases. 
A)  The apparent KM for the substrate increases. 
B)  The apparent KM for the substrate decreases. 
C)  The apparent Vmax for the substrate increases. 
D)  The apparent Vmax for the substrate decreases.

Question 9

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.

Question 10

In the concerted model the most active enzyme form will be when

Accepted Answer

A)  all subunits are in the R state. 
B)  all subunits are in the T state. 
C)  there is a 50:50 mix of R & T states. 
A)  all subunits are in the R state. 
B)  all subunits are in the T state. 
C)  there is a 50:50 mix of R & T states.

Question 11

Which of the following types of amino acids active is least likely to be involved in enzyme catalysis?

Accepted Answer

A)  Those with hydrophilic, neutral side-chains. 
B)  Those with negatively charged side-chains. 
C)  Those with positively charge side-chains. 
D)  Those with hydrocarbon side-chains. 
A)  Those with hydrophilic, neutral side-chains. 
B)  Those with negatively charged side-chains. 
C)  Those with positively charge side-chains. 
D)  Those with hydrocarbon side-chains.

Question 12

Metal ions play an important role in reaction mechanisms because

Accepted Answer

A)  they block the active site of enzymes so that inhibitors cannot bind. 
B)  they can act as Lewis acids. 
C)  water is excluded from the active site when metal ions are bound. 
D)  they prevent protein aggregation. 
A)  they block the active site of enzymes so that inhibitors cannot bind. 
B)  they can act as Lewis acids. 
C)  water is excluded from the active site when metal ions are bound. 
D)  they prevent protein aggregation.

Question 13

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 
A)  ATP inhibits and CTP activates 
B)  ATP activates and CTP inhibits 
C)  Both ATP and CTP inhibit 
D)  Both ATP and CTP activate

Question 14

Which of the following is a mechanism of regulating enzyme activity?

Accepted Answer

A)  Feedback inhibition by product. 
B)  Addition or removal of phosphate groups from of the enzyme. 
C)  Presence of activators. 
D)  Activation of zymogens. 
E)  All of these regulate enzyme activity. 
A)  Feedback inhibition by product. 
B)  Addition or removal of phosphate groups from of the enzyme. 
C)  Presence of activators. 
D)  Activation of zymogens. 
E)  All of these regulate enzyme activity.

Question 15

Which of the following does not apply to the concerted model for subunit behavior:

Accepted Answer

A)  Each subunit can exist in a relaxed (R) and taut (T) conformation. 
B)  All subunits will be in either the R or the T conformation at the same time. 
C)  Some subunits can be in the R state while others are in the T state. 
A)  Each subunit can exist in a relaxed (R) and taut (T) conformation. 
B)  All subunits will be in either the R or the T conformation at the same time. 
C)  Some subunits can be in the R state while others are in the T state.

Question 16

Enzymes that catalyze similar functions will invariably have

Accepted Answer

A)  similar overall structures. 
B)  serine in their active sites. 
C)  histidine in their active sites. 
D)  active sites that can catalyze the reactions in question. 
A)  similar overall structures. 
B)  serine in their active sites. 
C)  histidine in their active sites. 
D)  active sites that can catalyze the reactions in question.

Question 17

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. 
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.

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

An important step in elucidating the behavior of an enzyme is

Nicotinamide adenine dinucleotide is

Which of the following is not true about B vitamins?

In reactions catalyzed by allosteric enzymes

The concerted and sequential models for the behavior of allosteric enzymes differ in

In a comparison of allosteric and non-allosteric enzymes

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

What happens when a K-acting inhibitor is added to an allosteric enzyme system?

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

In the concerted model the most active enzyme form will be when

Which of the following types of amino acids active is least likely to be involved in enzyme catalysis?

Metal ions play an important role in reaction mechanisms because

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

Which of the following is a mechanism of regulating enzyme activity?

Which of the following does not apply to the concerted model for subunit behavior:

Enzymes that catalyze similar functions will invariably have

Phosphorylation and allosteric control of enzymes.

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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