Question 1

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. 
D)  none of these 
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. 
D)  none of these

Question 2

Enzyme kinetics falls into two general categories, simple saturation and cooperative kinetics.

Accepted Answer

A) True 
 B)False

Question 3

Which of the following is true about cocaine addiction

Accepted Answer

A)  it is easy to treat by using a drug that blocks a neurotransmitter receptor 
B)  it is based on release of the neurotransmitter GABA 
C)  it can be treated with catalytic antibodies 
D)  catalytic antibodies against coacaine are designed to mimic the cocaine molecule itself 
E)  none of these 
A)  it is easy to treat by using a drug that blocks a neurotransmitter receptor 
B)  it is based on release of the neurotransmitter GABA 
C)  it can be treated with catalytic antibodies 
D)  catalytic antibodies against coacaine are designed to mimic the cocaine molecule itself 
E)  none of these

Question 4

Labeling the amino acid residues in the active site of an enzyme requires

Accepted Answer

A)  a reagent structurally similar to the substrate. 
B)  a highly polar reagent. 
C)  a reagent that contains an aromatic group. 
D)  a reagent that contains a halogen atom. 
A)  a reagent structurally similar to the substrate. 
B)  a highly polar reagent. 
C)  a reagent that contains an aromatic group. 
D)  a reagent that contains a halogen atom.

Question 5

Phosphorylation of enzymes

Accepted Answer

A)  has no effect on their catalytic activity. 
B)  does not require ATP. 
C)  usually takes place on serine, threonine, and tyrosine residues. 
D)  always increases the activity of the enzyme 
A)  has no effect on their catalytic activity. 
B)  does not require ATP. 
C)  usually takes place on serine, threonine, and tyrosine residues. 
D)  always increases the activity of the enzyme

Question 6

In zymogen activation

Accepted Answer

A)  only digestive enzymes are involved. 
B)  a conformational change takes place with no alteration of primary structure. 
C)  an inactive protein is converted to an active one by bond cleavage. 
D)  there is aggregation of several enzyme molecules when the substrate binds. 
A)  only digestive enzymes are involved. 
B)  a conformational change takes place with no alteration of primary structure. 
C)  an inactive protein is converted to an active one by bond cleavage. 
D)  there is aggregation of several enzyme molecules when the substrate binds.

Question 7

Many metabolic pathways involve multistep reactions. Consider the following pathway.  
Which of the following would be an example of feedback inhibition?

Accepted Answer

A)  the product of the final reaction, F, interacting with E1. 
B)  F interacting with an allosteric site in E4. 
C)  B interacting with an allosteric site in E1. 
D)  all of the intermediates or products in the reaction interacting with the active site in E1. 
A)  the product of the final reaction, F, interacting with E1. 
B)  F interacting with an allosteric site in E4. 
C)  B interacting with an allosteric site in E1. 
D)  all of the intermediates or products in the reaction interacting with the active site in E1.

Question 8

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 9

The active site of chymotrypsin contains all of the following, except:

Accepted Answer

A)  Histidine residue. 
B)  A magnesium ion. 
C)  Hydrophobic pocket to bind the substrate. 
D)  Serine residue. 
E)  All of these are in the active site of chymotrypsin. 
A)  Histidine residue. 
B)  A magnesium ion. 
C)  Hydrophobic pocket to bind the substrate. 
D)  Serine residue. 
E)  All of these are in the active site of chymotrypsin.

Question 10

In the concerted model the binding of the first substrate molecule will achieve all except

Accepted Answer

A)  facilitation of the binding of other substrate molecules. 
B)  facilitation of the conversion of other subunits to the active state. 
C)  facilitation of the binding of inhibitors to the enzyme. 
D)  All of these are facilitated by the binding of the first substrate molecule. 
E)  None of these answers is correct. 
A)  facilitation of the binding of other substrate molecules. 
B)  facilitation of the conversion of other subunits to the active state. 
C)  facilitation of the binding of inhibitors to the enzyme. 
D)  All of these are facilitated by the binding of the first substrate molecule. 
E)  None of these answers is correct.

Question 11

The binding of aspartate to different subunits of ATCase is an example of

Accepted Answer

A)  enzyme inhibition 
B)  a heterotropic effect 
C)  a homotropic effect 
D)  negative cooperativity 
E)  none of these 
A)  enzyme inhibition 
B)  a heterotropic effect 
C)  a homotropic effect 
D)  negative cooperativity 
E)  none of these

Question 12

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 13

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 14

Which of the following is true?

Accepted Answer

A)  Allosteric enzymes are rarely important in the regulation of metabolic pathways. 
B)  Michaelis-Menten kinetics describe the reactions of allosteric enzymes 
C)  Allosteric enzymes have a hyperbolic plot of reaction rate vs. substrate concentration 
D)  none of these is true 
A)  Allosteric enzymes are rarely important in the regulation of metabolic pathways. 
B)  Michaelis-Menten kinetics describe the reactions of allosteric enzymes 
C)  Allosteric enzymes have a hyperbolic plot of reaction rate vs. substrate concentration 
D)  none of these is true

Question 15

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 16

CTP is a known inhibitor of ATCase, the enzyme that catalyzes the first reaction in the pathway for the synthesis of this compound. This is an example of

Accepted Answer

A)  irreversible inhibition 
B)  feedback inhibition 
C)  zymogenic inhibition 
D)  negative cooperativity 
A)  irreversible inhibition 
B)  feedback inhibition 
C)  zymogenic inhibition 
D)  negative cooperativity

Question 17

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 18

Which of the following is true about salicylate?

Accepted Answer

A)  it is a natural compound from the bark of a tree 
B)  it is structurally similar to aspirin 
C)  it stimulates the protein kinase, AMPK 
D)  it has therapeutic effects in lowering the risk of heart disease 
E)  all of these 
A)  it is a natural compound from the bark of a tree 
B)  it is structurally similar to aspirin 
C)  it stimulates the protein kinase, AMPK 
D)  it has therapeutic effects in lowering the risk of heart disease 
E)  all of these

Question 19

The vitamin biotin is involved in this type of reaction:

Accepted Answer

A)  Carboxylation reactions 
B)  Decarboxylation reactions 
C)  Redox reactions 
D)  Acyl transfer reactions 
E)  Transamination reactions 
A)  Carboxylation reactions 
B)  Decarboxylation reactions 
C)  Redox reactions 
D)  Acyl transfer reactions 
E)  Transamination reactions

Question 20

The behavior of allosteric enzymes

Accepted Answer

A)  does not play any role in feedback inhibition in metabolic pathways 
B)  is strongly dependent on the presence of metal ions 
C)  is related to their ability to hydrolyze themselves 
D)  depends on changes in their quaternary structure on binding of substrates or inhibitors 
A)  does not play any role in feedback inhibition in metabolic pathways 
B)  is strongly dependent on the presence of metal ions 
C)  is related to their ability to hydrolyze themselves 
D)  depends on changes in their quaternary structure on binding of substrates or inhibitors

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

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

Enzyme kinetics falls into two general categories, simple saturation and cooperative kinetics.

Which of the following is true about cocaine addiction

Labeling the amino acid residues in the active site of an enzyme requires

Phosphorylation of enzymes

In zymogen activation

Many metabolic pathways involve multistep reactions. Consider the following pathway. Which of the following would be an example of feedback inhibition?

Nicotinamide adenine dinucleotide is

The active site of chymotrypsin contains all of the following, except:

In the concerted model the binding of the first substrate molecule will achieve all except

The binding of aspartate to different subunits of ATCase is an example of

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

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

Which of the following is true?

Which of the following is not true about B vitamins?

CTP is a known inhibitor of ATCase, the enzyme that catalyzes the first reaction in the pathway for the synthesis of this compound. This is an example of

In reactions catalyzed by allosteric enzymes

Which of the following is true about salicylate?

The vitamin biotin is involved in this type of reaction:

The behavior of allosteric 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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