Question 1

Enzyme X catalyzes the addition of a hydroxyl group to substrate Y.In the process a metal cofactor is reduced and then reoxidized.What class of enzyme is X?

Accepted Answer

A) oxidoreductase 
B) ligase 
C) hydrolase 
D) isomerase 
E) lyase 
A) oxidoreductase 
B) ligase 
C) hydrolase 
D) isomerase 
E) lyase

Question 2

Which of the following is TRUE regarding cofactors?

Accepted Answer

A) Coenzymes are often separate from the enzyme and do not need recharged. 
B) Metal ions must be covalently attached to function as a cofactor. 
C) Cofactor is a broad term used for all enzyme "helpers". 
D) Prosthetic groups can dissociate readily and be regenerated for use in another enzyme. 
E) An apoenzyme implies that a cofactor is present. 
A) Coenzymes are often separate from the enzyme and do not need recharged. 
B) Metal ions must be covalently attached to function as a cofactor. 
C) Cofactor is a broad term used for all enzyme "helpers". 
D) Prosthetic groups can dissociate readily and be regenerated for use in another enzyme. 
E) An apoenzyme implies that a cofactor is present.

Question 3

Zymogens are not enzymatically active because

Accepted Answer

A) the active site amino acids have been mutated. 
B) they have not yet bound the proper cofactor. 
C) their environment has the wrong pH. 
D) they are not yet shaped such that essential proximity and orientation catalysis can occur. 
E) None of the above is correct. 
A) the active site amino acids have been mutated. 
B) they have not yet bound the proper cofactor. 
C) their environment has the wrong pH. 
D) they are not yet shaped such that essential proximity and orientation catalysis can occur. 
E) None of the above is correct.

Question 4

Simultaneous stimulation of a reaction by general acid and general base catalysis is defined as

Accepted Answer

A) covalent catalysis. 
B) electrostatic catalysis. 
C) proximity catalysis. 
D) concerted acid-base catalysis. 
E) transition state catalysis. 
A) covalent catalysis. 
B) electrostatic catalysis. 
C) proximity catalysis. 
D) concerted acid-base catalysis. 
E) transition state catalysis.

Question 5

Acid-base catalysis may be accomplished by:

Accepted Answer

A) active site specificity 
B) charge delocalization 
C) buffer effects 
D) induced strain 
E) conformational change 
A) active site specificity 
B) charge delocalization 
C) buffer effects 
D) induced strain 
E) conformational change

Question 6

An uncatalyzed reaction has a rate of 4.2 × 10-7 sec-1.When an enzyme is added the rate is 3.2 × 104 sec-1.Calculate the rate enhancement caused by the enzyme.

Accepted Answer

A) 3)2 × 104 
B) 7)4 × 10-3 
C) 1)3 × 10-2 
D) 7)6 × 1010 
E) The data are not appropriate for the calculation requested. 
A) 3)2 × 104 
B) 7)4 × 10-3 
C) 1)3 × 10-2 
D) 7)6 × 1010 
E) The data are not appropriate for the calculation requested.

Question 7

Which type of catalysis may be carried out using redistribution of electron density to facilitate the transfer of a proton?
(I)proximity
(II)acid-base
(III)covalent
(IV)strain

Accepted Answer

A) I 
B) II 
C) III 
D) II,III 
E) II,IV 
A) I 
B) II 
C) III 
D) II,III 
E) II,IV

Question 8

During the course of a catalytic reaction the following occurs: 1)Substrate is covalently bound and oriented with proximity to the active site residues.2)Negative charge builds up on the substrate and is stabilized.3)Oxidation of the enzyme followed by reduction to complete the catalytic cycle.What type of chemical species can facilitate these reactions?

Accepted Answer

A) nucleophilic amino acids 
B) electrophilic groups 
C) prosthetic phosphate groups 
D) transition metal anions 
E) transition metal cations 
A) nucleophilic amino acids 
B) electrophilic groups 
C) prosthetic phosphate groups 
D) transition metal anions 
E) transition metal cations

Question 9

A recent discovery has suggested that a gene mutation results in several amino acid substitutions within an active site.The following substitutions have been identified and are each expected to form the active site:
 
It was also noticed that a coenzyme molecule containing a hydroxyl (-OH)group binds to the mutated protein in approximately the same location as the original serine but does not alter the structure of the protein in anyway.Based on your knowledge of amino acids,enzymes,and catalysis,which of the following is a REASONABLE conclusion?

Accepted Answer

A) The mutant protein cleaves on the carboxy side of phenylalanine. 
B) The mutant protein cleaves peptide bonds on the carboxy side of glutamate or aspartate. 
C) The mutant protein cleaves peptide bonds on the carboxy side of lysine or arginine. 
D) The mutant protein functions identical to chymotrypsin. 
E) The mutant protein has no function. 
A) The mutant protein cleaves on the carboxy side of phenylalanine. 
B) The mutant protein cleaves peptide bonds on the carboxy side of glutamate or aspartate. 
C) The mutant protein cleaves peptide bonds on the carboxy side of lysine or arginine. 
D) The mutant protein functions identical to chymotrypsin. 
E) The mutant protein has no function.

Question 10

Why can histidine NOT act as a base in the lysosome (an organelle where the pH is close to 4.5)?

Accepted Answer

A) Histidine has a positive charge at pH 4.5. 
B) Histidine has a side chain pK close to 6. 
C) Histidine would be protonated at pH 4.5. 
D) All of the above are correct. 
E) None of the above is correct. 
A) Histidine has a positive charge at pH 4.5. 
B) Histidine has a side chain pK close to 6. 
C) Histidine would be protonated at pH 4.5. 
D) All of the above are correct. 
E) None of the above is correct.

Question 11

______ metals are the most common metallic enzyme cofactors.

Accepted Answer

A) Actinide 
B) Alkali 
C) Heavy 
D) Rare earth 
E) Transition 
A) Actinide 
B) Alkali 
C) Heavy 
D) Rare earth 
E) Transition

Question 12

Proximity effects

Accepted Answer

A) result from active site specificity. 
B) result from substrate channeling. 
C) result in increased effective concentration of substrate. 
D) lower the energy of activation. 
E) All of the above of the above are correct. 
A) result from active site specificity. 
B) result from substrate channeling. 
C) result in increased effective concentration of substrate. 
D) lower the energy of activation. 
E) All of the above of the above are correct.

Question 13

In affinity labeling,a technique used to study enzyme mechanisms,

Accepted Answer

A) A compound designed to bind at the active site reacts with and therefore permits the identification of a nearby group. 
B) A fluorescent group is attached to the substrate to identify the position of the active site. 
C) Highly purified enzyme is obtained by affinity chromatography for mechanistic studies. 
D) A radioactive isotope is incorporated into the substrate to identify the position of the active site. 
E) Genetic modification of amino acid residues is used to alter the binding affinity of the active site. 
A) A compound designed to bind at the active site reacts with and therefore permits the identification of a nearby group. 
B) A fluorescent group is attached to the substrate to identify the position of the active site. 
C) Highly purified enzyme is obtained by affinity chromatography for mechanistic studies. 
D) A radioactive isotope is incorporated into the substrate to identify the position of the active site. 
E) Genetic modification of amino acid residues is used to alter the binding affinity of the active site.

Enzyme X catalyzes the addition of a hydroxyl group to substrate Y.In the process a metal cofactor is reduced and then reoxidized.What class of enzyme is X?

Which of the following is TRUE regarding cofactors?

Zymogens are not enzymatically active because

Simultaneous stimulation of a reaction by general acid and general base catalysis is defined as

Acid-base catalysis may be accomplished by:

An uncatalyzed reaction has a rate of 4.2 × 10^-7 sec^-1.When an enzyme is added the rate is 3.2 × 10⁴ sec^-1.Calculate the rate enhancement caused by the enzyme.

Which type of catalysis may be carried out using redistribution of electron density to facilitate the transfer of a proton? (I)proximity (II)acid-base (III)covalent (IV)strain

Why can histidine NOT act as a base in the lysosome (an organelle where the pH is close to 4.5)?

______ metals are the most common metallic enzyme cofactors.

Proximity effects

In affinity labeling,a technique used to study enzyme mechanisms,

Introduction to the Chemistry of Life

Water

Nucleotides, nucleic Acids, and Genetic Information

Amino Acids

Proteins: Primary Structure

Proteins: Three-Dimensional Structure

Protein Function Part I: Myoglobin and Hemoglobin

Carbohydrates

Lipids and Biological Membranes

Membrane Transport

Enzyme Kinetics, inhibition and Control

Biochemical Signaling

Introduction to Metabolism

Glucose Catabolism

Glycogen Metabolism and Gluconeogenesis

Citric Acid Cycle

Electron Transport and Oxidative Phosphorylation

Photosynthesis

Lipid Metabolism

Amino Acid Metabolism

Mammalian Fuel Metabolism: Integration and Regulation

Nucleotide Metabolism

Nucleic Acid Structure

DNA Replication, repair and Recombination

Transcription and Rna Processing

Protein Synthesis

Regulation of Gene Expression

Filters

Exam 11: Enzyme Catalysis

Enzyme X catalyzes the addition of a hydroxyl group to substrate Y.In the process a metal cofactor is reduced and then reoxidized.What class of enzyme is X?

Which of the following is TRUE regarding cofactors?

Zymogens are not enzymatically active because

Simultaneous stimulation of a reaction by general acid and general base catalysis is defined as

Acid-base catalysis may be accomplished by:

An uncatalyzed reaction has a rate of 4.2 × 10-7 sec-1.When an enzyme is added the rate is 3.2 × 104 sec-1.Calculate the rate enhancement caused by the enzyme.

Which type of catalysis may be carried out using redistribution of electron density to facilitate the transfer of a proton? (I)proximity (II)acid-base (III)covalent (IV)strain

Why can histidine NOT act as a base in the lysosome (an organelle where the pH is close to 4.5)?

______ metals are the most common metallic enzyme cofactors.

Proximity effects

In affinity labeling,a technique used to study enzyme mechanisms,

Introduction to the Chemistry of Life

Water

Nucleotides, nucleic Acids, and Genetic Information

Amino Acids

Proteins: Primary Structure

Proteins: Three-Dimensional Structure

Protein Function Part I: Myoglobin and Hemoglobin

Carbohydrates

Lipids and Biological Membranes

Membrane Transport

Enzyme Kinetics, inhibition and Control

Biochemical Signaling

Introduction to Metabolism

Glucose Catabolism

Glycogen Metabolism and Gluconeogenesis

Citric Acid Cycle

Electron Transport and Oxidative Phosphorylation

Photosynthesis

Lipid Metabolism

Amino Acid Metabolism

Mammalian Fuel Metabolism: Integration and Regulation

Nucleotide Metabolism

Nucleic Acid Structure

DNA Replication, repair and Recombination

Transcription and Rna Processing

Protein Synthesis

Regulation of Gene Expression

Filters

An uncatalyzed reaction has a rate of 4.2 × 10^-7 sec^-1.When an enzyme is added the rate is 3.2 × 10⁴ sec^-1.Calculate the rate enhancement caused by the enzyme.