Question 1

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 2

The main distinguishing feature of the concerted model for the behavior of allosteric enzymes is that

Accepted Answer

A)  the conformation of all subunits changes simultaneously. 
B)  it applies only to dimeric enzymes. 
C)  it involves three possible conformations for all subunits. 
D)  the T and R conformations exist in roughly equal amounts. 
A)  the conformation of all subunits changes simultaneously. 
B)  it applies only to dimeric enzymes. 
C)  it involves three possible conformations for all subunits. 
D)  the T and R conformations exist in roughly equal amounts.

Question 3

The pH profile of an enzyme can help identify specific amino acids in the active site because:

Accepted Answer

A)  all enzymes have a pH optimum 
B)  only the active site amino acids can detect changes in pH 
C)  acidic and basic amino acids are often involved in the active site and pH changes can change their ability to catalyze a reaction 
D)  the pH optimum is always the pI of the most critical amino acid in the active site 
A)  all enzymes have a pH optimum 
B)  only the active site amino acids can detect changes in pH 
C)  acidic and basic amino acids are often involved in the active site and pH changes can change their ability to catalyze a reaction 
D)  the pH optimum is always the pI of the most critical amino acid in the active site

Question 4

Which of the following best describes negative cooperativity?

Accepted Answer

A)  Binding of one substrate molecule prevents the enzyme from working at all. 
B)  Binding of one substrate molecule inhibits the binding of a second substrate. 
C)  Binding of one substrate molecule enhances the binding of a second substrate. 
D)  Binding of one substrate molecule inhibits the binding of other effectors. 
A)  Binding of one substrate molecule prevents the enzyme from working at all. 
B)  Binding of one substrate molecule inhibits the binding of a second substrate. 
C)  Binding of one substrate molecule enhances the binding of a second substrate. 
D)  Binding of one substrate molecule inhibits the binding of other effectors.

Question 5

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 6

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 7

Which of the following statements about coenzymes is true?

Accepted Answer

A)  They are commonly derived from vitamins. 
B)  They bind to the active site region on specific types of enzymes. 
C)  They can be metal ions, such as Zn(II). 
D)  NAD+, FAD and biotin are all examples of coenzymes. 
E)  All of these statements are true. 
A)  They are commonly derived from vitamins. 
B)  They bind to the active site region on specific types of enzymes. 
C)  They can be metal ions, such as Zn(II). 
D)  NAD+, FAD and biotin are all examples of coenzymes. 
E)  All of these statements are true.

Question 8

Where do allosteric inhibitors bind on an enzyme?

Accepted Answer

A)  They always bind at a site different from the active site. 
B)  They always bind at the active site. 
C)  They can bind at either active site or another site. 
D)  They always bind directly to the substrate 
E)  none of these 
A)  They always bind at a site different from the active site. 
B)  They always bind at the active site. 
C)  They can bind at either active site or another site. 
D)  They always bind directly to the substrate 
E)  none of these

Question 9

Which groups of amino acids are most likely to be found in the active site of an enzyme?

Accepted Answer

A)  leucine, lysine, alanine. 
B)  cysteine, isoleucine, phenylalanine. 
C)  tyrosine, threonine, leucine. 
D)  serine, histidine, aspartate. 
A)  leucine, lysine, alanine. 
B)  cysteine, isoleucine, phenylalanine. 
C)  tyrosine, threonine, leucine. 
D)  serine, histidine, aspartate.

Question 10

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 11

Homotrophic effects for allosteric enzymes involve

Accepted Answer

A)  the same molecule binding to different sites in the enzyme. 
B)  different molecules binding to the same site in an enzyme. 
C)  different molecules binding to different sites in the same enzyme. 
D)  All of these are homotrophic effects. 
A)  the same molecule binding to different sites in the enzyme. 
B)  different molecules binding to the same site in an enzyme. 
C)  different molecules binding to different sites in the same enzyme. 
D)  All of these are homotrophic effects.

Question 12

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 13

The term K0.5 is analogous to the KM

Accepted Answer

A) True 
 B)False

Question 14

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 15

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 16

$\text { Exhibit 7A }$

-Refer to Exhibit 7A. Which two enzymes would be the most likely ones to regulate if this pathway is freely reversible and can go both ways?

Accepted Answer

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

Question 17

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 18

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 19

$\text { Exhibit 7A }$

-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 20

Redox 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

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

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

The main distinguishing feature of the concerted model for the behavior of allosteric enzymes is that

The pH profile of an enzyme can help identify specific amino acids in the active site because:

Which of the following best describes negative cooperativity?

Enzymes that catalyze similar functions will invariably have

An important step in elucidating the behavior of an enzyme is

Which of the following statements about coenzymes is true?

Where do allosteric inhibitors bind on an enzyme?

Which groups of amino acids are most likely to be found in the active site of an enzyme?

Important mechanisms of enzymatic catalysis include

Homotrophic effects for allosteric enzymes involve

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

The term K0.5 is analogous to the KM

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

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

Exhibit 7A \text { Exhibit 7A } Exhibit 7A -Refer to Exhibit 7A. Which two enzymes would be the most likely ones to regulate if this pathway is freely reversible and can go both ways?

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

Metal ions play an important role in reaction mechanisms because

Exhibit 7A \text { Exhibit 7A } Exhibit 7A -Refer to Exhibit 7A. The final product, R, will most likely inhibit which reaction?

Redox reactions often use this cofactor:

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

Filters

The term K_0.5 is analogous to the K_M

$\text { Exhibit 7A }$ $\text { Exhibit 7A } -Refer to Exhibit 7A. The final product, R, will most likely inhibit which reaction?$ -Refer to Exhibit 7A. The final product, R, will most likely inhibit which reaction?