Question 1

Which of the following elements is involved in the mechanism of chymotrypsin?

Accepted Answer

A) deprotonation of an active site Asp residue by His to start the reaction 
B) formation of an acyl-enzyme intermediate that must be hydrolyzed to complete the reaction 
C) stabilization of the positively charged His by a Gln residue 
D) direct deprotonation of water by His to generate a hydroxide ion for initiation of the reaction 
A) deprotonation of an active site Asp residue by His to start the reaction 
B) formation of an acyl-enzyme intermediate that must be hydrolyzed to complete the reaction 
C) stabilization of the positively charged His by a Gln residue 
D) direct deprotonation of water by His to generate a hydroxide ion for initiation of the reaction

Question 2

Which of the following regarding the hydrolysis of p-nitrophenyl acetate by chymotrypsin is correct?

Accepted Answer

A) The active site contains a serine residue,an unprotonated histidine,and an unprotonated aspartate residue at pH 7.0 prior to binding the substrate. 
B) The first product is acetic acid. 
C) An actyl-enzyme tetrahedral intermediate forms during the mechanism. 
D) Attack of a water molecule on the acyl-enzyme intermediate yields the first product. 
A) The active site contains a serine residue,an unprotonated histidine,and an unprotonated aspartate residue at pH 7.0 prior to binding the substrate. 
B) The first product is acetic acid. 
C) An actyl-enzyme tetrahedral intermediate forms during the mechanism. 
D) Attack of a water molecule on the acyl-enzyme intermediate yields the first product.

Question 3

Which of the following types of serine protease inhibitors are organic fluorophosphates?

Accepted Answer

A) competitive 
B) uncompetitive 
C) non-competitive 
D) irreversible 
A) competitive 
B) uncompetitive 
C) non-competitive 
D) irreversible

Question 4

Which of the following is NOT relevant to the reaction catalyzed by chorismate mutase?

Accepted Answer

A) The reaction involves a concerted intramolecular rearrangement of chorismate to prephenate during the synthesis of phenylalanine. 
B) The enzyme-catalyzed and uncatalyzed reactions follow almost identical routes. 
C) The enzymatic reaction is thought to involve transition-state stabilization by 12 electrostatic and hydrogen bond interactions. 
D) The geometry of the enzyme active site is such that the difference in energy between ES and the near attack conformation is more than 100 kJ/mol. 
A) The reaction involves a concerted intramolecular rearrangement of chorismate to prephenate during the synthesis of phenylalanine. 
B) The enzyme-catalyzed and uncatalyzed reactions follow almost identical routes. 
C) The enzymatic reaction is thought to involve transition-state stabilization by 12 electrostatic and hydrogen bond interactions. 
D) The geometry of the enzyme active site is such that the difference in energy between ES and the near attack conformation is more than 100 kJ/mol.

Question 5

Which of the following will increase the energy level of ES and subsequently the enzyme-catalyzed reaction rate?

Accepted Answer

A) stabilization of ES by solvation 
B) destabilization of ES by strain 
C) stabilization of ES by hydrophobic effects 
D) destabilization of ES by electrostatic effects 
A) stabilization of ES by solvation 
B) destabilization of ES by strain 
C) stabilization of ES by hydrophobic effects 
D) destabilization of ES by electrostatic effects

Question 6

Which of the following inhibitors is effective as a transition-state analog?

Accepted Answer

A) competitive 
B) non-competitive 
C) allosteric 
D) irreversible 
A) competitive 
B) non-competitive 
C) allosteric 
D) irreversible

Question 7

How does HIV-1 protease differ from most mammalian aspartic acid proteases?

Accepted Answer

A) It has 2 subunits,each with a 2-aspartate active site. 
B) It has 2 subunits,each contributing an aspartate to the active site. 
C) It has 2 active sites on 1 protein. 
D) It has 2 subunits,1 with an active site and the other with a regulatory activity. 
A) It has 2 subunits,each with a 2-aspartate active site. 
B) It has 2 subunits,each contributing an aspartate to the active site. 
C) It has 2 active sites on 1 protein. 
D) It has 2 subunits,1 with an active site and the other with a regulatory activity.

Which of the following elements is involved in the mechanism of chymotrypsin?

Which of the following regarding the hydrolysis of p-nitrophenyl acetate by chymotrypsin is correct?

Which of the following types of serine protease inhibitors are organic fluorophosphates?

Which of the following is NOT relevant to the reaction catalyzed by chorismate mutase?

Which of the following will increase the energy level of ES and subsequently the enzyme-catalyzed reaction rate?

Which of the following inhibitors is effective as a transition-state analog?

How does HIV-1 protease differ from most mammalian aspartic acid proteases?

The Facts of Life: Chemistry Is the Logic of Biological Phenomena

Water: the Medium of Life

Thermodynamics of Biological Systems

Amino Acids

Proteins: Their Primary Structure and Biological Functions

Proteins: Secondary, tertiary, and Quaternary Structure

Carbohydrates and the Glycoconjugates of Cell Surfaces

Lipids

Lipid Biosynthesis

Membranes and Membrane Transport

The Reception and Transmission of Extracellular Information

Enzymes Kinetics and Specificity

Enzyme Regulation

Molecular Motors

Nutrition and the Organization of Metabolism

Glycolysis

The Tricarboxylic Acid Cycle

Electron Transport and Oxidative Phosphorylation

Photosynthesis

Gluconeogenesis, glycogen Metabolism, and the Pentose Phosphate Pathway

Fatty Acid Catabolism

Nitrogen Acquisition and Amino Acid Metabolism

Nucleotides and Nucleic Acids

Structure of Nucleic Acids

Synthesis and Degradation of Nucleotides

Recombinant Dna: Cloning and Creation of Chimeric Genes

DNA Metabolism: Replication, recombination, and Repair

Transcription and the Regulation of Gene Expression

Protein Synthesis

Post-Transcriptional Regulation of Gene Expression

Completing the Protein Life Cycle: Folding, processing, and Degradation

Metabolic Integration and Organ Specialization

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Exam 13: Mechanisms of Enzyme Action

Which of the following elements is involved in the mechanism of chymotrypsin?

Which of the following regarding the hydrolysis of p-nitrophenyl acetate by chymotrypsin is correct?

Which of the following types of serine protease inhibitors are organic fluorophosphates?

Which of the following is NOT relevant to the reaction catalyzed by chorismate mutase?

Which of the following will increase the energy level of ES and subsequently the enzyme-catalyzed reaction rate?

Which of the following inhibitors is effective as a transition-state analog?

How does HIV-1 protease differ from most mammalian aspartic acid proteases?

The Facts of Life: Chemistry Is the Logic of Biological Phenomena

Water: the Medium of Life

Thermodynamics of Biological Systems

Amino Acids

Proteins: Their Primary Structure and Biological Functions

Proteins: Secondary, tertiary, and Quaternary Structure

Carbohydrates and the Glycoconjugates of Cell Surfaces

Lipids

Lipid Biosynthesis

Membranes and Membrane Transport

The Reception and Transmission of Extracellular Information

Enzymes Kinetics and Specificity

Enzyme Regulation

Molecular Motors

Nutrition and the Organization of Metabolism

Glycolysis

The Tricarboxylic Acid Cycle

Electron Transport and Oxidative Phosphorylation

Photosynthesis

Gluconeogenesis, glycogen Metabolism, and the Pentose Phosphate Pathway

Fatty Acid Catabolism

Nitrogen Acquisition and Amino Acid Metabolism

Nucleotides and Nucleic Acids

Structure of Nucleic Acids

Synthesis and Degradation of Nucleotides

Recombinant Dna: Cloning and Creation of Chimeric Genes

DNA Metabolism: Replication, recombination, and Repair

Transcription and the Regulation of Gene Expression

Protein Synthesis

Post-Transcriptional Regulation of Gene Expression

Completing the Protein Life Cycle: Folding, processing, and Degradation

Metabolic Integration and Organ Specialization

Filters