Question 1

Procathepsin B is a lysosomal protease that is first translated as a proenzyme.On autocleavage it is fully activated.Procathepsin B is

Accepted Answer

A)  a zymogen. 
B)  in the T state after autocleavage. 
C)  an allosteric enzyme. 
D)  inactive at low pH. 
A)  a zymogen. 
B)  in the T state after autocleavage. 
C)  an allosteric enzyme. 
D)  inactive at low pH.

Question 2

Below is a Lineweaver-Burk plot in which the axis labels have been removed.Interpret the plot to determine the vmax.

Accepted Answer

A)  0.2 
B)  5 
C)  3 
D)  0.33 
A)  0.2 
B)  5 
C)  3 
D)  0.33

Question 3

An enzyme that requires the coenzyme nicotinamide adenine dinucleotide belongs to which enzyme class?

Accepted Answer

A)  transferases 
B)  isomerases 
C)  ligases 
D)  oxidoreductases 
A)  transferases 
B)  isomerases 
C)  ligases 
D)  oxidoreductases

Question 4

Binding of glucose to hexokinase causes a conformational change in the enzyme.This is an example of the __________ model of enzyme catalysis.

Accepted Answer

A)  substrate-induced 
B)  lock and key 
C)  induced-fit 
D)  glove and hand 
A)  substrate-induced 
B)  lock and key 
C)  induced-fit 
D)  glove and hand

Question 5

Glutamine synthetase is in the R state when Tyr397 is

Accepted Answer

A)  deadenylated. 
B)  uridylated. 
C)  phosphorylated. 
D)  dephosphorylated. 
A)  deadenylated. 
B)  uridylated. 
C)  phosphorylated. 
D)  dephosphorylated.

Question 6

The conversion of L-proline to D-proline is shown below.Which of the following characteristics would most likely be found in a transition state analog that inhibits an enzyme that catalyzes the reaction?

Accepted Answer

A)  planar 
B)  positively charged at the $\alpha$-carbon 
C)  tetrahedral geometry at the $\alpha$-carbon 
D)  double bonds within the ring 
A)  planar 
B)  positively charged at the $\alpha$-carbon 
C)  tetrahedral geometry at the $\alpha$-carbon 
D)  double bonds within the ring

Question 7

Which of the following is an assumption made when using Michaelis-Menten kinetics?

Accepted Answer

A)  The conversion of E + P  ES does not occur. 
B)  k1 > k2 
C)  v0 = vmax at low [S] 
D)  The conversion of EP  E + P is rapid. 
A)  The conversion of E + P  ES does not occur. 
B)  k1 > k2 
C)  v0 = vmax at low [S] 
D)  The conversion of EP  E + P is rapid.

Question 8

When compared with the T state of aspartate transcarbamoylase,the R state

Accepted Answer

A)  has dissociated into two C3R3 complexes. 
B)  has greater separation of the catalytic subunits. 
C)  is bound to CTP. 
D)  has substrate bound in the ATP binding site. 
A)  has dissociated into two C3R3 complexes. 
B)  has greater separation of the catalytic subunits. 
C)  is bound to CTP. 
D)  has substrate bound in the ATP binding site.

Question 9

Which answer correctly classifies the compound with its relationship to aspartate transcarbamoylase?

Accepted Answer

A)  ATP; allosteric inhibitor 
B)  ATP; allosteric activator 
C)  CTP; allosteric activator 
D)  CTP; substrate 
A)  ATP; allosteric inhibitor 
B)  ATP; allosteric activator 
C)  CTP; allosteric activator 
D)  CTP; substrate

Question 10

Which of the following is true of the tetrahedral intermediate in the chymotrypsin mechanism?

Accepted Answer

A)  It is lower in free energy than the substrate. 
B)  It is partially positively charged. 
C)  All bonds are the same length. 
D)  It contains an oxyanion. 
A)  It is lower in free energy than the substrate. 
B)  It is partially positively charged. 
C)  All bonds are the same length. 
D)  It contains an oxyanion.

Question 11

In the figure below,KM is indicated at

Accepted Answer

A)  A. 
B)  B. 
C)  C. 
D)  D. 
A)  A. 
B)  B. 
C)  C. 
D)  D.

Question 12

An experiment is performed in which the kinetics of an enzyme-catalyzed reaction at different pHs is monitored.It is found that the Km does not change but that the kcat increases as the pH goes above 7.Which of the following is true?

Accepted Answer

A)  A chemical group within the enzyme that has a pKa of around 7 is likely involved in the catalytic mechanism. 
B)  A chemical group with a pKa of around 7 must be deprotonated in order for substrate to bind. 
C)  A chemical group with a pKa of around 7 must be positively charged in order for the substrate to bind. 
D)  Protons are acting as positive heterotropic allosteric effectors of this enzyme. 
A)  A chemical group within the enzyme that has a pKa of around 7 is likely involved in the catalytic mechanism. 
B)  A chemical group with a pKa of around 7 must be deprotonated in order for substrate to bind. 
C)  A chemical group with a pKa of around 7 must be positively charged in order for the substrate to bind. 
D)  Protons are acting as positive heterotropic allosteric effectors of this enzyme.

Question 13

A plot of vo versus [S] for aspartyl transcarbamoylase displays three sigmoidal lines.If the line in the middle represents the enzyme activity in the absence of any allosteric effectors,then the line to the __________ represents the enzyme in the __________ when bound to __________.

Accepted Answer

A)  right; R state; CTP 
B)  right; T state; CTP 
C)  left; R state; GTP 
D)  left; T state; GTP 
A)  right; R state; CTP 
B)  right; T state; CTP 
C)  left; R state; GTP 
D)  left; T state; GTP

Question 14

The catalytic triad of chymotrypsin is composed of His57,Ser195,and

Accepted Answer

A)  Gly193. 
B)  Glu103. 
C)  Asp120. 
D)  Asp102. 
A)  Gly193. 
B)  Glu103. 
C)  Asp120. 
D)  Asp102.

Question 15

Enzyme active sites

Accepted Answer

A)  are nonspecific. 
B)  are a pocket or cleft. 
C)  always exclude water. 
D)  can only bind a single substrate at a time. 
A)  are nonspecific. 
B)  are a pocket or cleft. 
C)  always exclude water. 
D)  can only bind a single substrate at a time.

Question 16

The regulation of a biomolecule through the addition or removal of a molecular tag involves __________ reactions.

Accepted Answer

A)  coenzyme-dependent redox 
B)  reversible covalent modification 
C)  metabolite transformation 
D)  isomerization 
A)  coenzyme-dependent redox 
B)  reversible covalent modification 
C)  metabolite transformation 
D)  isomerization

Question 17

The y-axis of a Lineweaver-Burk plot is

Accepted Answer

A)  v0. 
B)  1 / vo. 
C)  Km / vmax. 
D)  1 / [S]. 
A)  v0. 
B)  1 / vo. 
C)  Km / vmax. 
D)  1 / [S].

Question 18

Propose an experiment to determine the presence of a predicted hydrophobic channel in a newly discovered enzyme.At your disposal you have the purified enzyme,the ability to analyze the enzyme by X-ray crystallography,a spectrophotometer,the enzyme substrate,and polyethylene glycol.Be sure to explain how the results will determine if the protein contains a hydrophobic channel.

Accepted Answer

To determine the presence of a predicted

Question 19

Connect the use of v0 to the ability to treat k-2 as negligible in Michaelis-Menten kinetics.

Accepted Answer

By considering the reaction at an early

Question 20

On a plot of [product] versus time for an enzyme-catalyzed reaction,the v0 is equal to the

Accepted Answer

A)  slope of the line / [S]. 
B)  [P] at the lowest time point. 
C)  slope of the line. 
D)  y-intercept. 
A)  slope of the line / [S]. 
B)  [P] at the lowest time point. 
C)  slope of the line. 
D)  y-intercept.

Exam 7: Enzyme Mechanisms

Procathepsin B is a lysosomal protease that is first translated as a proenzyme.On autocleavage it is fully activated.Procathepsin B is

Below is a Lineweaver-Burk plot in which the axis labels have been removed.Interpret the plot to determine the vmax.

An enzyme that requires the coenzyme nicotinamide adenine dinucleotide belongs to which enzyme class?

Binding of glucose to hexokinase causes a conformational change in the enzyme.This is an example of the __________ model of enzyme catalysis.

Glutamine synthetase is in the R state when Tyr397 is

The conversion of L-proline to D-proline is shown below.Which of the following characteristics would most likely be found in a transition state analog that inhibits an enzyme that catalyzes the reaction?

Which of the following is an assumption made when using Michaelis-Menten kinetics?

When compared with the T state of aspartate transcarbamoylase,the R state

Which answer correctly classifies the compound with its relationship to aspartate transcarbamoylase?

Which of the following is true of the tetrahedral intermediate in the chymotrypsin mechanism?

In the figure below,KM is indicated at

An experiment is performed in which the kinetics of an enzyme-catalyzed reaction at different pHs is monitored.It is found that the Km does not change but that the kcat increases as the pH goes above 7.Which of the following is true?

A plot of vo versus [S] for aspartyl transcarbamoylase displays three sigmoidal lines.If the line in the middle represents the enzyme activity in the absence of any allosteric effectors,then the line to the __________ represents the enzyme in the __________ when bound to __________.

The catalytic triad of chymotrypsin is composed of His57,Ser195,and

Enzyme active sites

The regulation of a biomolecule through the addition or removal of a molecular tag involves __________ reactions.

The y-axis of a Lineweaver-Burk plot is

Connect the use of v0 to the ability to treat k-2 as negligible in Michaelis-Menten kinetics.

On a plot of [product] versus time for an enzyme-catalyzed reaction,the v0 is equal to the

Principles of Biochemistry

Physical Biochemistry: Energy Conversion,water,and Membranes

Nucleic Acid Structure and Function

Protein Structure

Methods in Protein Biochemistry

Protein Function

Cell Signaling Systems

Glycolysis: a Paradigm of Metabolic Regulation

The Citrate Cycle

Oxidative Phosphorylation

Photosynthesis

Carbohydrate Structure and Function

Carbohydrate Metabolism

Lipid Structure and Function

Lipid Metabolism

Amino Acid Metabolism

Nucleotide Metabolism

Metabolic Integration

Dna Replication, repair, and Recombination

Rna Synthesis, processing, and Gene Silencing

Protein Synthesis, posttranslational Modification, and Transport

Gene Regulation

Filters

Below is a Lineweaver-Burk plot in which the axis labels have been removed.Interpret the plot to determine the v_max.

In the figure below,K_M is indicated at

An experiment is performed in which the kinetics of an enzyme-catalyzed reaction at different pHs is monitored.It is found that the K_m does not change but that the k_cat increases as the pH goes above 7.Which of the following is true?

A plot of v_o versus [S] for aspartyl transcarbamoylase displays three sigmoidal lines.If the line in the middle represents the enzyme activity in the absence of any allosteric effectors,then the line to the represents the enzyme in the when bound to __.

Connect the use of v₀ to the ability to treat k_-2 as negligible in Michaelis-Menten kinetics.

On a plot of [product] versus time for an enzyme-catalyzed reaction,the v₀ is equal to the