Question 1

Which of the following reactions is catalyzed by a kinase?

Accepted Answer

A)  glycerol + ATP  glycerol phosphate + ADP 
B)  lactate + NAD+  pyruvate + NADH + H+ 
C)  glucose 6-phosphate  fructose 6-phosphate 
D)  UDP-galactose + glucose 1-phosphate  UDP-glucose + galactose 1-phosphate 
E)  fructose 1,6-bisphosphate + H2O  fructose 6-phosphate + Pi 
A)  glycerol + ATP  glycerol phosphate + ADP 
B)  lactate + NAD+  pyruvate + NADH + H+ 
C)  glucose 6-phosphate  fructose 6-phosphate 
D)  UDP-galactose + glucose 1-phosphate  UDP-glucose + galactose 1-phosphate 
E)  fructose 1,6-bisphosphate + H2O  fructose 6-phosphate + Pi

Question 2

All of the following statements about the Michaelis constant are correct EXCEPT which one?

Accepted Answer

A)  For many enzymes, Km approximates the equilibrium constant for the conversion of ES to E and P. 
B)  A low value for Km is generally associated with a high affinity of an E for an S. 
C)  Km is calculated from the intersection, in a Lineweaver-Burk plot, of the experimentally determined line with the horizontal axis. 
D)  Km may be defined as the substrate concentration which gives half-maximal velocity. 
E)  At a substrate concentration equal to Km, half of the total number of enzyme molecules may be present as an ES complex. 
A)  For many enzymes, Km approximates the equilibrium constant for the conversion of ES to E and P. 
B)  A low value for Km is generally associated with a high affinity of an E for an S. 
C)  Km is calculated from the intersection, in a Lineweaver-Burk plot, of the experimentally determined line with the horizontal axis. 
D)  Km may be defined as the substrate concentration which gives half-maximal velocity. 
E)  At a substrate concentration equal to Km, half of the total number of enzyme molecules may be present as an ES complex.

Question 3

A proteolytic enzyme such as trypsin is an example of

Accepted Answer

A)  an oxidoreductase. 
B)  a hydrolase. 
C)  a transferase. 
D)  an isomerase. 
E)  a ligase. 
A)  an oxidoreductase. 
B)  a hydrolase. 
C)  a transferase. 
D)  an isomerase. 
E)  a ligase.

Question 4

The amino acid containing a group that can readily act as a general acid-base catalyst at pH7 is

Accepted Answer

A)  proline. 
B)  lysine. 
C)  arginine. 
D)  asparagine. 
E)  histidine. 
A)  proline. 
B)  lysine. 
C)  arginine. 
D)  asparagine. 
E)  histidine.

Question 5

In the regulation of an overall metabolic sequence, which of the following reactions is most likely to be modulated by allosteric effectors?

Accepted Answer

A)  Any reaction of the sequence. 
B)  the last reaction of the sequence. 
C)  The last reaction of the sequence. 
D)  The fastest reaction of the sequence. 
E)  The slowest reaction of the sequence. 
A)  Any reaction of the sequence. 
B)  the last reaction of the sequence. 
C)  The last reaction of the sequence. 
D)  The fastest reaction of the sequence. 
E)  The slowest reaction of the sequence.

Question 6

In a Lineweaver-Burke plot, 1 / V vs 1 / [S], the slope of the plot is equal to

Accepted Answer

A)  Km / Vmax. 
B)  Km. 
C)  1/Vmax. 
D)  1/Km. 
E)  Vmax. 
A)  Km / Vmax. 
B)  Km. 
C)  1/Vmax. 
D)  1/Km. 
E)  Vmax.

Question 7

Where on the diagram above would the plot of a K class allosteric inhibitor coincide with the plot of a competitive inhibitor?

Accepted Answer

A)  A 
B)  B 
C)  C 
D)  D 
E)  E 
A)  A 
B)  B 
C)  C 
D)  D 
E)  E

Question 8

What is the reaction rate in a simple enzymatic system, if the substrate concentration is much less than Km?

Accepted Answer

A)  It is maximal. 
B)  It would be too slow to measure. 
C)  It would be reduced by addition of more substrate. 
D)  It would be uninfluenced by the addition of more substrate. 
E)  It is virtually proportional to substrate concentration. 
A)  It is maximal. 
B)  It would be too slow to measure. 
C)  It would be reduced by addition of more substrate. 
D)  It would be uninfluenced by the addition of more substrate. 
E)  It is virtually proportional to substrate concentration.

Question 9

Regulation of enzyme activity by allosteric effectors

Accepted Answer

A)  can only increase enzyme activity. 
B)  can only decrease activity. 
C)  usually involves monomeric enzymes. 
D)  involves an equilibrium between two conformational forms of an enzyme. 
E)  requires covalent attachment of the effector to the enzyme. 
A)  can only increase enzyme activity. 
B)  can only decrease activity. 
C)  usually involves monomeric enzymes. 
D)  involves an equilibrium between two conformational forms of an enzyme. 
E)  requires covalent attachment of the effector to the enzyme.

Question 10

Which of the following factors can be significant in enzyme catalysis?

Accepted Answer

A)  induced fit 
B)  distortion or strain in the substrate 
C)  general acid-base catalysis 
D)  covalent catalysis 
E)  all of the above are correct 
A)  induced fit 
B)  distortion or strain in the substrate 
C)  general acid-base catalysis 
D)  covalent catalysis 
E)  all of the above are correct

Question 11

In the presence of a typical noncompetitive inhibitor of the activity of a particular enzyme toward a given substrate

Accepted Answer

A)  the enzyme is irreversibly inactivated. 
B)  the potential maximum velocity will remain unchanged from that in the absence of the inhibitor. 
C)  the interaction of the inhibitor with the substrate is a major factor leading to the inhibition observed. 
D)  sigmoidal kinetics would be expected if there is no change in protein conformation on the binding of either S or I. 
E)  the apparent Michaelis constant for the substrate will be the same with or without inhibitor present. 
A)  the enzyme is irreversibly inactivated. 
B)  the potential maximum velocity will remain unchanged from that in the absence of the inhibitor. 
C)  the interaction of the inhibitor with the substrate is a major factor leading to the inhibition observed. 
D)  sigmoidal kinetics would be expected if there is no change in protein conformation on the binding of either S or I. 
E)  the apparent Michaelis constant for the substrate will be the same with or without inhibitor present.

Question 12

A derivative of thiamine participates as a coenzyme in

Accepted Answer

A)  the conversion of pyruvate to oxaloacetate. 
B)  reactions involving the decarboxylation of alpha-keto acids. 
C)  the conversions of glucose to glucuronic acid. 
D)  the transamination of alpha-amino acids. 
E)  the conversion of methylmalonyl-CoA to succinyl-CoA. 
A)  the conversion of pyruvate to oxaloacetate. 
B)  reactions involving the decarboxylation of alpha-keto acids. 
C)  the conversions of glucose to glucuronic acid. 
D)  the transamination of alpha-amino acids. 
E)  the conversion of methylmalonyl-CoA to succinyl-CoA.

Question 13

The Hill relationship can be used to determine the

Accepted Answer

A)  reversibility of a reaction. 
B)  number of independent binding sites on a protein for a ligand. 
C)  the number of cooperative binding sites in a protein for a single ligand. 
D)  whether an effector is homotropic or heterotropic. 
E)  oxygen binding capacity of a protein. 
A)  reversibility of a reaction. 
B)  number of independent binding sites on a protein for a ligand. 
C)  the number of cooperative binding sites in a protein for a single ligand. 
D)  whether an effector is homotropic or heterotropic. 
E)  oxygen binding capacity of a protein.

Question 14

The influence of pH on the rate of enzymatic reactions may be a result of

Accepted Answer

A)  a requirement that the substrate be in a definite ionic form. 
B)  a requirement for specific ionic groups on the enzyme protein for enzyme activity. 
C)  a requirement for specific groups which do not dissociate at any pH. 
D)  all of the above. 
E)  A and B only. 
A)  a requirement that the substrate be in a definite ionic form. 
B)  a requirement for specific ionic groups on the enzyme protein for enzyme activity. 
C)  a requirement for specific groups which do not dissociate at any pH. 
D)  all of the above. 
E)  A and B only.

Question 15

Which of the following methods are used to regulate enzyme activity?

Accepted Answer

A)  covalent modification 
B)  competitive inhibition 
C)  allosteric regulation 
D)  synthesis and degradation of the enzyme 
E)  all of the above are used to regulate enzyme activity 
A)  covalent modification 
B)  competitive inhibition 
C)  allosteric regulation 
D)  synthesis and degradation of the enzyme 
E)  all of the above are used to regulate enzyme activity

Question 16

An example of reversible covalent modification of an enzyme is

Accepted Answer

A)  ADP-ribosylation. 
B)  glycosylation. 
C)  phosphorylation. 
D)  allosteric modification. 
E)  interaction with cAMP. 
A)  ADP-ribosylation. 
B)  glycosylation. 
C)  phosphorylation. 
D)  allosteric modification. 
E)  interaction with cAMP.

Question 17

In a two substrate-two product enzymatic reaction, the apparent Km for one of the substrates is

Accepted Answer

A)  independent of the concentration of the other substrate. 
B)  dependent upon the concentration of the products. 
C)  dependent upon the concentration of the other substrate. 
D)  dependent upon the concentration of enzyme. 
E)  dependent upon the maximum velocity. 
A)  independent of the concentration of the other substrate. 
B)  dependent upon the concentration of the products. 
C)  dependent upon the concentration of the other substrate. 
D)  dependent upon the concentration of enzyme. 
E)  dependent upon the maximum velocity.

Question 18

What is an allosteric effector of an enzymic reaction?

Accepted Answer

A)  A competitive inhibitor. 
B)  An uncompetitive inhibitor. 
C)  A substance which affects enzymic activity by binding to a site other than the substrate binding site. 
D)  A denaturant of the enzyme. 
E)  A substance which binds to the substrate and thus makes it unavailable to the enzyme. 
A)  A competitive inhibitor. 
B)  An uncompetitive inhibitor. 
C)  A substance which affects enzymic activity by binding to a site other than the substrate binding site. 
D)  A denaturant of the enzyme. 
E)  A substance which binds to the substrate and thus makes it unavailable to the enzyme.

Question 19

A substrate molecule that causes a conformational change in the enzyme at or near the active site would be best described by which of the listed mechanisms?

Accepted Answer

A)  Induced fit 
B)  Destabilization 
C)  Acid Base Catalysis 
D)  Covalent catalysis 
E)  none of the above 
A)  Induced fit 
B)  Destabilization 
C)  Acid Base Catalysis 
D)  Covalent catalysis 
E)  none of the above

Question 20

The vitamin which functions as the coenzyme (or part of the coenzyme) for a variety of reactions of the type, RH + carbon dioxide --> R-COOH, is

Accepted Answer

A)  biotin. 
B)  pyridoxine. 
C)  pantothenate. 
D)  B12. 
E)  folate. 
A)  biotin. 
B)  pyridoxine. 
C)  pantothenate. 
D)  B12. 
E)  folate.

Exam 10: Enzymes: Classification, Kinetics, and Control

Which of the following reactions is catalyzed by a kinase?

All of the following statements about the Michaelis constant are correct EXCEPT which one?

A proteolytic enzyme such as trypsin is an example of

The amino acid containing a group that can readily act as a general acid-base catalyst at pH7 is

In the regulation of an overall metabolic sequence, which of the following reactions is most likely to be modulated by allosteric effectors?

In a Lineweaver-Burke plot, 1 / V vs 1 / [S], the slope of the plot is equal to

Where on the diagram above would the plot of a K class allosteric inhibitor coincide with the plot of a competitive inhibitor?

What is the reaction rate in a simple enzymatic system, if the substrate concentration is much less than Km?

Regulation of enzyme activity by allosteric effectors

Which of the following factors can be significant in enzyme catalysis?

In the presence of a typical noncompetitive inhibitor of the activity of a particular enzyme toward a given substrate

A derivative of thiamine participates as a coenzyme in

The Hill relationship can be used to determine the

The influence of pH on the rate of enzymatic reactions may be a result of

Which of the following methods are used to regulate enzyme activity?

An example of reversible covalent modification of an enzyme is

In a two substrate-two product enzymatic reaction, the apparent Km for one of the substrates is

What is an allosteric effector of an enzymic reaction?

A substrate molecule that causes a conformational change in the enzyme at or near the active site would be best described by which of the listed mechanisms?

The vitamin which functions as the coenzyme (or part of the coenzyme) for a variety of reactions of the type, RH + carbon dioxide --> R-COOH, is

Eukaryotic Cell Structure

DNA and RNA: Composition and Structure

Protein I: Composition and Structure

DNA Replication, Recombination, and Repair

RNA: Transcription and Rna Processing

Protein Synthesis: Translation and Posttranslational Modifications

Recombinant Dna and Biotechnology

Regulation of Gene Expression

Protein II: Structure-Function Relationships in Protein Families

The Cytochromes P450 and Nitric Oxide Synthases

Biological Membranes: Structure and Membrane Transport

Fundamentals of Signal Transduction

Bioenergetics and Oxidative Metabolism

Carbohydrate Metabolism I: Major Metabolic Pathways and Their Control

Carbohydrate Metabolism II: Special Pathways and Glycoconjugates

Lipid Metabolism I: Synthesis, Storage, and Utilization of Fatty Acids and Triacylglycerols

Lipid Metabolism II: Pathways of Metabolism of Special Lipids

Amino Acid Metabolism

Purine and Pyrimidine Nucleotide Metabolism

Metabolic Interrelationships

Biochemistry of Hormones

Molecular Cell Biology

Cell Cycle, Programmed Cell Death, and Cancer

Digestion and Absorption of Basic Nutritional Constituents

Digestion and Absorption of Basic Nutritional Constituents

Principles of Nutrition I and II

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