Question 1

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 2

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 3

ATP is a negative allosteric effector for glycogen phosporylase. This is an example of

Accepted Answer

A)  feedback inhibition. 
B)  positive cooperativity. 
C)  negative cooperativity. 
D)  competitive inhibition. 
A)  feedback inhibition. 
B)  positive cooperativity. 
C)  negative cooperativity. 
D)  competitive inhibition.

Question 4

A velocity curve (V vs. [S]) for a typical allosteric enzyme will be

Accepted Answer

A)  a rectangular hyperbola. 
B)  a sigmoid curve. 
C)  a straight line. 
D)  a parabola. 
E)  none of these 
A)  a rectangular hyperbola. 
B)  a sigmoid curve. 
C)  a straight line. 
D)  a parabola. 
E)  none of these

Question 5

According to the concerted model of allosteric behavior, an allosteric activator

Accepted Answer

A)  favors the taut (tight) form of the enzyme. 
B)  favors the relaxed form of the enzyme. 
C)  can only bind to the enzyme if the substrate is already bound. 
D)  can only bind to the enzyme if the substrate has not already bound. 
A)  favors the taut (tight) form of the enzyme. 
B)  favors the relaxed form of the enzyme. 
C)  can only bind to the enzyme if the substrate is already bound. 
D)  can only bind to the enzyme if the substrate has not already bound.

Question 6

Which of the following substances can modify the quaternary structure and the behavior of a protein such as aspartate transcarbamoylase (ATCase) by binding to it?

Accepted Answer

A)  Apoplastic effectors 
B)  Bacterial effectors 
C)  Allosteric effectors 
D)  Cytoplasmic effectors 
A)  Apoplastic effectors 
B)  Bacterial effectors 
C)  Allosteric effectors 
D)  Cytoplasmic effectors

Question 7

Important mechanisms of enzymatic catalysis include

Accepted Answer

A)  nucleophilic reactions 
B)  general acid-base catalysis 
C)  Lewis acid-base catalysis 
D)  all of these 
A)  nucleophilic reactions 
B)  general acid-base catalysis 
C)  Lewis acid-base catalysis 
D)  all of these

Question 8

Is the Michaelis-Menten equation useful when studying allosteric enzymes?

Accepted Answer

A)  Yes 
B)  No 
C)  Only if the enzyme displays positive cooperativity. 
D)  Only if the enzyme displays negative cooperativity. 
A)  Yes 
B)  No 
C)  Only if the enzyme displays positive cooperativity. 
D)  Only if the enzyme displays negative cooperativity.

Question 9

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 10

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 11

Exhibit 7A   Refer to Exhibit 7A. The final product, R, will most likely inhibit which reaction?

Accepted Answer

A)  1 
B)  2 
C)  3 
D)  4 
E)  5 
A)  1 
B)  2 
C)  3 
D)  4 
E)  5

Question 12

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 13

The serine in the active site of chymotrypsin functions as

Accepted Answer

A)  a Lewis acid. 
B)  a metal ion. 
C)  an electrophile. 
D)  a nucleophile. 
A)  a Lewis acid. 
B)  a metal ion. 
C)  an electrophile. 
D)  a nucleophile.

Question 14

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 15

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 16

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.

Question 17

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 18

Which of the following types of amino acids in an active site 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 19

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 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 a comparison of allosteric and non-allosteric enzymes

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

ATP is a negative allosteric effector for glycogen phosporylase. This is an example of

A velocity curve (V vs. [S]) for a typical allosteric enzyme will be

According to the concerted model of allosteric behavior, an allosteric activator

Which of the following substances can modify the quaternary structure and the behavior of a protein such as aspartate transcarbamoylase (ATCase) by binding to it?

Important mechanisms of enzymatic catalysis include

Is the Michaelis-Menten equation useful when studying allosteric enzymes?

The concerted model for allosteric behavior was proposed by:

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

Exhibit 7A Refer to Exhibit 7A. The final product, R, will most likely inhibit which reaction?

Which of the following is true?

The serine in the active site of chymotrypsin functions as

Which of the following is true about cocaine addiction

In zymogen activation

Zymogens are

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

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

In reactions catalyzed by allosteric enzymes

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 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

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