Question 1

From the diagram above which amino acid is necessary for catalysis of this reaction?

Accepted Answer

A)  Protonated asp 
B)  Protonated lys 
C)  Unprotonated arg 
D)  Unprotonated his 
E)  Unprotonated tyr 
A)  Protonated asp 
B)  Protonated lys 
C)  Unprotonated arg 
D)  Unprotonated his 
E)  Unprotonated tyr D

Question 2

Which one of the following enzyme types would be involved in the conversion of an aldosugar to a ketosugar?

Accepted Answer

A)  A kinase 
B)  A mutase 
C)  An enolase 
D)  A dehydrogenase 
E)  An isomerase 
A)  A kinase 
B)  A mutase 
C)  An enolase 
D)  A dehydrogenase 
E)  An isomerase E

Question 3

The cofactor for transamination is

Accepted Answer

A)  nicotinamide. 
B)  biotin. 
C)  thiamine pyrophosphate. 
D)  pyridoxal phosphate. 
E)  vitamin B12. 
A)  nicotinamide. 
B)  biotin. 
C)  thiamine pyrophosphate. 
D)  pyridoxal phosphate. 
E)  vitamin B12. D

Question 4

The effect of pH on enzyme-catalyzed reactions can be related to all of the following EXCEPT

Accepted Answer

A)  the influence of pH on the equilibrium. 
B)  the need for certain forms of ionizable groups on the substrate. 
C)  the need for certain forms of ionizable groups in the enzyme. 
D)  the general effect of pH on protein structure. 
E)  the influence of pH on the interaction of hydrophobic residues in the protein. 
A)  the influence of pH on the equilibrium. 
B)  the need for certain forms of ionizable groups on the substrate. 
C)  the need for certain forms of ionizable groups in the enzyme. 
D)  the general effect of pH on protein structure. 
E)  the influence of pH on the interaction of hydrophobic residues in the protein.

Question 5

Coenzymes are derived from many vitamins. Which of the following is derived from vitamin B6 (niacin)

Accepted Answer

A)  tetrahydrofolic acid 
B)  nicotinamide adenine dinucleotide (NA
D)  
C)  pyridoxal phosphate 
D)  flavin adenine dinucleotide (FA
D)  
E)  coenzyme A (CoASH) 
A)  tetrahydrofolic acid 
B)  nicotinamide adenine dinucleotide (NA
D)  
C)  pyridoxal phosphate 
D)  flavin adenine dinucleotide (FA
D)  
E)  coenzyme A (CoASH)

Question 6

Chymotrypsin is classified as a(n)

Accepted Answer

A)  oxidoreductase. 
B)  transferase. 
C)  hydrolase. 
D)  lyase. 
E)  ligase. 
A)  oxidoreductase. 
B)  transferase. 
C)  hydrolase. 
D)  lyase. 
E)  ligase.

Question 7

In the case of noncompetitive inhibition

Accepted Answer

A)  the inhibitor generally resembles the substrate. 
B)  the inhibition can be overcome by raising the substrate concentration. 
C)  Ki is the concentration of inhibitor required for half maximal inhibition. 
D)  a high Ki means that the inhibitor has a high affinity for the enzyme. 
E)  the inhibitor is commonly the product of the enzymatic reaction. 
A)  the inhibitor generally resembles the substrate. 
B)  the inhibition can be overcome by raising the substrate concentration. 
C)  Ki is the concentration of inhibitor required for half maximal inhibition. 
D)  a high Ki means that the inhibitor has a high affinity for the enzyme. 
E)  the inhibitor is commonly the product of the enzymatic reaction.

Question 8

For Michaelis-Menten kinetics, Vmax is

Accepted Answer

A)  proportional to k1. 
B)  given in units of moles/liter. 
C)  the velocity which is observed when the substrate concentration is one half of Km. 
D)  proportional to k2. 
E)  none of the above. 
A)  proportional to k1. 
B)  given in units of moles/liter. 
C)  the velocity which is observed when the substrate concentration is one half of Km. 
D)  proportional to k2. 
E)  none of the above.

Question 9

Km is:

Accepted Answer

A)  the concentration of an inhibitor needed to give 1/2 Vmax 
B)  a measure of the rate of product formation 
C)  related to the affinity of the enzyme for its substrate 
D)  a measure of the activation energy of the enzyme-catalyzed reaction 
E)  the velocity equal to one-half of the maximum velocity 
A)  the concentration of an inhibitor needed to give 1/2 Vmax 
B)  a measure of the rate of product formation 
C)  related to the affinity of the enzyme for its substrate 
D)  a measure of the activation energy of the enzyme-catalyzed reaction 
E)  the velocity equal to one-half of the maximum velocity

Question 10

The initial velocity condition in the derivation of the Michaelis-Menten expression

Accepted Answer

A)  allows measurement of product formation near equilibrium. 
B)  may not be attainable if the equilibrium constant is very large in favor of product formation. 
C)  requires that measurements be made before product accumulates significantly. 
D)  requires that the enzyme-substrate complex be formed very slowly. 
E)  none of the above 
A)  allows measurement of product formation near equilibrium. 
B)  may not be attainable if the equilibrium constant is very large in favor of product formation. 
C)  requires that measurements be made before product accumulates significantly. 
D)  requires that the enzyme-substrate complex be formed very slowly. 
E)  none of the above

Question 11

In the presence of an irreversible inhibitor

Accepted Answer

A)  Km will be increased. 
B)  Vmax will be increased. 
C)  Km will be decreased. 
D)  Vmax will be decreased. 
E)  neither Km nor Vmax will change. 
A)  Km will be increased. 
B)  Vmax will be increased. 
C)  Km will be decreased. 
D)  Vmax will be decreased. 
E)  neither Km nor Vmax will change.

Question 12

For the reaction A---> B, catalyst I has an activation energy of 1400 calories per mol. Catalyst II has an activation energy of 2800 calories per mol.

Accepted Answer

A)  catalyst II is more efficient. 
B)  catalyst I is more efficient. 
C)  both catalysts should have about the same catalytic efficiency. 
D)  one cannot determine which is more efficient without information about Delta Ho for the reaction. 
A)  catalyst II is more efficient. 
B)  catalyst I is more efficient. 
C)  both catalysts should have about the same catalytic efficiency. 
D)  one cannot determine which is more efficient without information about Delta Ho for the reaction.

Question 13

In considering the 'active site' of enzymes, a fair generalization is that

Accepted Answer

A)  nearly all the amino acid side-chains of the protein must directly participate in catalysis. 
B)  all the amino acid residues which are involved in the active site are adjacent because they are located on the same short stretch of the polypeptide backbone. 
C)  the conformation of the active site region does not exist at all until the substrate is bound. 
D)  the amino acid residues which form the active site are in close proximity because of the specific three-dimensional conformation the protein has adopted. 
E)  only one amino acid residue is involved in the active site. 
A)  nearly all the amino acid side-chains of the protein must directly participate in catalysis. 
B)  all the amino acid residues which are involved in the active site are adjacent because they are located on the same short stretch of the polypeptide backbone. 
C)  the conformation of the active site region does not exist at all until the substrate is bound. 
D)  the amino acid residues which form the active site are in close proximity because of the specific three-dimensional conformation the protein has adopted. 
E)  only one amino acid residue is involved in the active site.

Question 14

Isoenzymes are

Accepted Answer

A)  proteolytic enzymes which are activated by the hydrolysis of a part of the peptide chain. 
B)  proteins without enzymatic activity which are necessary to activate enzyme proteins. 
C)  enzymes containing identical amino acid compositions and sequences but which catalyzed different reaction. 
D)  different enzymes which catalyze the same reaction. 
E)  enzymes which catalyze several different reactions. 
A)  proteolytic enzymes which are activated by the hydrolysis of a part of the peptide chain. 
B)  proteins without enzymatic activity which are necessary to activate enzyme proteins. 
C)  enzymes containing identical amino acid compositions and sequences but which catalyzed different reaction. 
D)  different enzymes which catalyze the same reaction. 
E)  enzymes which catalyze several different reactions.

Question 15

Which one of the following statements about the maximum velocity (Vmax) of an enzyme catalyzed reaction is true?

Accepted Answer

A)  Vmax is unaltered in the presence of a noncompetitive inhibitor. 
B)  Vmax is directly proportional to enzyme concentration. 
C)  Vmax is directly proportional to substrate concentration. 
D)  Vmax is directly proportional to the measured rate (v). 
E)  Vmax is directly proportional to Km, being higher for enzymes with higher Km values for their substrates. 
A)  Vmax is unaltered in the presence of a noncompetitive inhibitor. 
B)  Vmax is directly proportional to enzyme concentration. 
C)  Vmax is directly proportional to substrate concentration. 
D)  Vmax is directly proportional to the measured rate (v). 
E)  Vmax is directly proportional to Km, being higher for enzymes with higher Km values for their substrates.

Question 16

The oligomeric structure of all lactate dehydrogenase isozymes is a

Accepted Answer

A)  monomer. 
B)  dimer. 
C)  trimer. 
D)  tetramer. 
E)  pentamer. 
A)  monomer. 
B)  dimer. 
C)  trimer. 
D)  tetramer. 
E)  pentamer.

Question 17

The oxidation and reduction of NAD occurs on which of the following?

Accepted Answer

A)  the adenine ring 
B)  the phosphoester bonds 
C)  the side-chain nitrogen of nicotinamide 
D)  the pyridine ring of nicotinamide 
E)  a ribose hydroxyl 
A)  the adenine ring 
B)  the phosphoester bonds 
C)  the side-chain nitrogen of nicotinamide 
D)  the pyridine ring of nicotinamide 
E)  a ribose hydroxyl

Question 18

Which of the following represents a protein modification which changes enzyme activity in a non-reversible manner?

Accepted Answer

A)  Competitive inhibition 
B)  Zymogen activation 
C)  Phosphorylation of a serine residue of the protein 
D)  coenzyme activation 
E)  allosteric activation 
A)  Competitive inhibition 
B)  Zymogen activation 
C)  Phosphorylation of a serine residue of the protein 
D)  coenzyme activation 
E)  allosteric activation

Question 19

Which of the following is LEAST likely to affect the Vmax of an enzyme?

Accepted Answer

A)  A change in pH 
B)  A change in temperature 
C)  Addition of a noncompetitive inhibitor 
D)  Addition of a competitive inhibitor 
E)  Addition of an irreversible inhibitor 
A)  A change in pH 
B)  A change in temperature 
C)  Addition of a noncompetitive inhibitor 
D)  Addition of a competitive inhibitor 
E)  Addition of an irreversible inhibitor

Question 20

For any enzymatic reaction, when the ratio of enzyme substrate complex to free enzyme [ES]/[E] increases.

Accepted Answer

A)  The velocity of the reaction will increase. 
B)  The velocity of the reaction will decrease. 
C)  The Km is increased. 
D)  The turnover number decreases. 
E)  An allosteric effector must be present. 
A)  The velocity of the reaction will increase. 
B)  The velocity of the reaction will decrease. 
C)  The Km is increased. 
D)  The turnover number decreases. 
E)  An allosteric effector must be present.

Exam 10: Enzymes: Classification, Kinetics, and Control

From the diagram above which amino acid is necessary for catalysis of this reaction?

Which one of the following enzyme types would be involved in the conversion of an aldosugar to a ketosugar?

The cofactor for transamination is

The effect of pH on enzyme-catalyzed reactions can be related to all of the following EXCEPT

Coenzymes are derived from many vitamins. Which of the following is derived from vitamin B6 (niacin)

Chymotrypsin is classified as a(n)

In the case of noncompetitive inhibition

For Michaelis-Menten kinetics, Vmax is

Km is:

The initial velocity condition in the derivation of the Michaelis-Menten expression

In the presence of an irreversible inhibitor

For the reaction A---> B, catalyst I has an activation energy of 1400 calories per mol. Catalyst II has an activation energy of 2800 calories per mol.

In considering the 'active site' of enzymes, a fair generalization is that

Isoenzymes are

Which one of the following statements about the maximum velocity (Vmax) of an enzyme catalyzed reaction is true?

The oligomeric structure of all lactate dehydrogenase isozymes is a

The oxidation and reduction of NAD occurs on which of the following?

Which of the following represents a protein modification which changes enzyme activity in a non-reversible manner?

Which of the following is LEAST likely to affect the Vmax of an enzyme?

For any enzymatic reaction, when the ratio of enzyme substrate complex to free enzyme [ES]/[E] increases.

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

Filters

Coenzymes are derived from many vitamins. Which of the following is derived from vitamin B₆ (niacin)