Question 1

Which of the following is seen in a reaction coordinate diagram for an enzyme-catalyzed reaction that uses covalent catalysis?

Accepted Answer

A)  an intermediate 
B)  two distinct transition states 
C)  reactants that are lower in energy than an intermediate 
D)  products that are lower in energy than an intermediate 
E)  all of the above 
A)  an intermediate 
B)  two distinct transition states 
C)  reactants that are lower in energy than an intermediate 
D)  products that are lower in energy than an intermediate 
E)  all of the above

Question 2

In the chymotrypsin mechanism, what is used to stabilize the negative charge on the carbonyl oxygen of the transition state?

Accepted Answer

A)  hydrogen bonding between the enzyme and the anion from the carbonyl oxygen 
B)  electrostatic interaction of the positively charged His and carbonyl oxygen 
C)  electrostatic interaction of the negatively charged Asp and carbonyl oxygen 
D)  electrostatic interaction of the active site Zn2+ and carbonyl oxygen 
E)  all of the above 
A)  hydrogen bonding between the enzyme and the anion from the carbonyl oxygen 
B)  electrostatic interaction of the positively charged His and carbonyl oxygen 
C)  electrostatic interaction of the negatively charged Asp and carbonyl oxygen 
D)  electrostatic interaction of the active site Zn2+ and carbonyl oxygen 
E)  all of the above

Question 3

Name one protease inhibited by antithrombin.

Accepted Answer

factor IXa

Question 4

When the transition state is formed, what is the specific interaction observed between Asp and His that helps stabilize the transition state?

Accepted Answer

A)  dipole-dipole interaction 
B)  electrostatic interaction 
C)  hydrogen bond 
D)  low-barrier hydrogen bond 
E)  covalent bond 
A)  dipole-dipole interaction 
B)  electrostatic interaction 
C)  hydrogen bond 
D)  low-barrier hydrogen bond 
E)  covalent bond

Question 5

Chymotrypsin has a large specificity pocket to bind the aromatic amino acids while elastase has a very small specificity pocket meant to bind Ala or Gly. Which of the following amino acid substitutions changes the specificity pocket of chymotrypsin to that of elastase?

Accepted Answer

A)  Trp  $\rarr$ Ser 
B)  Leu  $\rarr$ Ala 
C)  Gly  $\rarr$  Val 
D)  Lys  $\rarr$  Asp 
E)  Val  $\rarr$  Asn 
A)  Trp  $\rarr$ Ser 
B)  Leu  $\rarr$ Ala 
C)  Gly  $\rarr$  Val 
D)  Lys  $\rarr$  Asp 
E)  Val  $\rarr$  Asn

Question 6

What amino acid residue present in the specificity pocket allows trypsin to bind to peptides containing Arg or Lys?

Accepted Answer

A)  Ser 
B)  His 
C)  Lys 
D)  Val 
E)  Asp 
A)  Ser 
B)  His 
C)  Lys 
D)  Val 
E)  Asp

Question 7

Heparin enhances the activity of ___ by acting as ___.

Accepted Answer

antithromb

Question 8

During the first half of the chymotrypsin mechanism where the acyl-enzyme intermediate is formed, what role does His play?

Accepted Answer

A)  general acid only 
B)  general base only 
C)  general acid then general base 
D)  general base then general acid 
E)  nucleophile 
A)  general acid only 
B)  general base only 
C)  general acid then general base 
D)  general base then general acid 
E)  nucleophile

Question 9

How does a catalyst affect the overall $\Delta$G of an endergonic reaction?

Accepted Answer

A)  it has no effect 
B)  the reaction becomes more endergonic 
C)  the reaction has a $\Delta$G of zero 
D)  the reaction becomes exergonic 
E)  none of the above 
A)  it has no effect 
B)  the reaction becomes more endergonic 
C)  the reaction has a $\Delta$G of zero 
D)  the reaction becomes exergonic 
E)  none of the above

Which of the following is seen in a reaction coordinate diagram for an enzyme-catalyzed reaction that uses covalent catalysis?

In the chymotrypsin mechanism, what is used to stabilize the negative charge on the carbonyl oxygen of the transition state?

Name one protease inhibited by antithrombin.

When the transition state is formed, what is the specific interaction observed between Asp and His that helps stabilize the transition state?

Chymotrypsin has a large specificity pocket to bind the aromatic amino acids while elastase has a very small specificity pocket meant to bind Ala or Gly. Which of the following amino acid substitutions changes the specificity pocket of chymotrypsin to that of elastase?

What amino acid residue present in the specificity pocket allows trypsin to bind to peptides containing Arg or Lys?

Heparin enhances the activity of _ by acting as _.

During the first half of the chymotrypsin mechanism where the acyl-enzyme intermediate is formed, what role does His play?

How does a catalyst affect the overall $\Delta$ G of an endergonic reaction?

The Chemical Basis of Life

Aqueous Chemistry

Nucleic Acid Structure and Function

Protein Structure

Protein Function

Enzyme Kinetics and Inhibition

Lipids and Membranes

Membrane Transport

Signaling

Carbohydrates

Metabolism and Bioenergetics

Glucose Metabolism

The Citric Acid Cycle

Oxidative Phosphorylation

Photosynthesis

Lipid Metabolism

Nitrogen Metabolism

Regulation of Mammalian Fuel Metabolism

DNA Replication and Repair

Transcription and RNA

Protein Synthesis

Filters

Exam 6: How Enzymes Work

Which of the following is seen in a reaction coordinate diagram for an enzyme-catalyzed reaction that uses covalent catalysis?

In the chymotrypsin mechanism, what is used to stabilize the negative charge on the carbonyl oxygen of the transition state?

Name one protease inhibited by antithrombin.

When the transition state is formed, what is the specific interaction observed between Asp and His that helps stabilize the transition state?

Chymotrypsin has a large specificity pocket to bind the aromatic amino acids while elastase has a very small specificity pocket meant to bind Ala or Gly. Which of the following amino acid substitutions changes the specificity pocket of chymotrypsin to that of elastase?

What amino acid residue present in the specificity pocket allows trypsin to bind to peptides containing Arg or Lys?

Heparin enhances the activity of ___ by acting as ___.

During the first half of the chymotrypsin mechanism where the acyl-enzyme intermediate is formed, what role does His play?

How does a catalyst affect the overall Δ\DeltaΔ G of an endergonic reaction?

The Chemical Basis of Life

Aqueous Chemistry

Nucleic Acid Structure and Function

Protein Structure

Protein Function

Enzyme Kinetics and Inhibition

Lipids and Membranes

Membrane Transport

Signaling

Carbohydrates

Metabolism and Bioenergetics

Glucose Metabolism

The Citric Acid Cycle

Oxidative Phosphorylation

Photosynthesis

Lipid Metabolism

Nitrogen Metabolism

Regulation of Mammalian Fuel Metabolism

DNA Replication and Repair

Transcription and RNA

Protein Synthesis

Filters

Heparin enhances the activity of _ by acting as _.

How does a catalyst affect the overall $\Delta$ G of an endergonic reaction?