Question 1

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

Question 2

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 3

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 4

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. 
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.

Question 5

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. 
A)  a nucleophile. 
B)  an electrophile. 
C)  a base. 
D)  a methyl donor.

Question 6

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 7

The vitamin pantothenic acid 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 8

The amino acids in the active site can be involved in all of these processes,except:

Accepted Answer

A)  Binding of the substrate. 
B)  Becoming part of the product of the reaction. 
C)  The actual chemical mechanism for the reaction. 
D)  Binding of some necessary cofactor for the reaction. 
E)  All of these can be functions of the amino acids in the active site 
A)  Binding of the substrate. 
B)  Becoming part of the product of the reaction. 
C)  The actual chemical mechanism for the reaction. 
D)  Binding of some necessary cofactor for the reaction. 
E)  All of these can be functions of the amino acids in the active site

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

The sequential model for allosteric behavior

Accepted Answer

A)  cannot account for reactions that display negative cooperativity. 
B)  postulates binding of substrates and inhibitors by the induced-fit model. 
C)  requires that the conformation of all subunits change simultaneously. 
D)  is mathematically simpler than the concerted model. 
A)  cannot account for reactions that display negative cooperativity. 
B)  postulates binding of substrates and inhibitors by the induced-fit model. 
C)  requires that the conformation of all subunits change simultaneously. 
D)  is mathematically simpler than the concerted model.

Question 11

Inhibitors which bind covalently to specific amino acids are useful in determining which amino acids are in the active site of an enzyme.

Accepted Answer

A) True 
 B)False

Question 12

In the concerted model,which state binds the substrate more tightly?

Accepted Answer

A)  the relaxed (R) state 
B)  the taut (T) state 
C)  Both states bind equally well. 
A)  the relaxed (R) state 
B)  the taut (T) state 
C)  Both states bind equally well.

Question 13

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

Accepted Answer

A) True 
 B)False

Question 14

How are cofactors bound to their enzymes?

Accepted Answer

A)  always covalently 
B)  always non-covalently 
C)  either covalently or non-covalently 
A)  always covalently 
B)  always non-covalently 
C)  either covalently or non-covalently

Question 15

Which of the following is unlikely to occur in binding of a substrate to an enzyme?

Accepted Answer

A)  stereospecific interactions. 
B)  hydrogen bonding. 
C)  adsorption to surfaces of metallic catalysts. 
D)  interactions with metal-ions. 
A)  stereospecific interactions. 
B)  hydrogen bonding. 
C)  adsorption to surfaces of metallic catalysts. 
D)  interactions with metal-ions.

Question 16

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 17

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

Question 18

In the concerted model for allosteric enzymes

Accepted Answer

A)  the relative affinities of substrate for the T and R conformations plays an important role in the cooperativity of the reaction. 
B)  the equilibrium between the T and R conformations plays a minor role. 
C)  the enzymatic activity of the T conformation is considerably higher than that of the R form. 
D)  it is possible to describe the reactions of all allosteric enzymes accurately. 
A)  the relative affinities of substrate for the T and R conformations plays an important role in the cooperativity of the reaction. 
B)  the equilibrium between the T and R conformations plays a minor role. 
C)  the enzymatic activity of the T conformation is considerably higher than that of the R form. 
D)  it is possible to describe the reactions of all allosteric enzymes accurately.

Question 19

Kinases usually transfer phosphates from

Accepted Answer

A)  ATP. 
B)  inorganic phosphate. 
C)  NADP+/NADPH. 
D)  amino acids. 
A)  ATP. 
B)  inorganic phosphate. 
C)  NADP+/NADPH. 
D)  amino acids.

Question 20

The sequential model for allosteric enzymes 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

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

Redox reactions often use this cofactor:

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

Acyl transfer reactions often use this cofactor:

Where do allosteric inhibitors bind on an enzyme?

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

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

The vitamin pantothenic acid is involved in this type of reaction:

The amino acids in the active site can be involved in all of these processes,except:

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

The sequential model for allosteric behavior

Inhibitors which bind covalently to specific amino acids are useful in determining which amino acids are in the active site of an enzyme.

In the concerted model,which state binds the substrate more tightly?

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

How are cofactors bound to their enzymes?

Which of the following is unlikely to occur in binding of a substrate to an enzyme?

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

The behavior of allosteric enzymes

In the concerted model for allosteric enzymes

Kinases usually transfer phosphates from

The sequential model for allosteric enzymes was proposed by:

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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