Question 1

All are characteristics of the enzyme hexokinase EXCEPT:

Accepted Answer

A)  It is not highly specific and will catalyze phosphorylation of a number of hexoses at the six position. 
B)  Hexoses bind the active site and induce a solvent inaccessible fit to the hexose. 
C)  Glycerol may fit into the active site, but it does not bind to induce a conformational change necessary for catalysis. 
D)  When a hexose binds the active site, the active site is modified to promote changes in the substrate to a transitional-state intermediate. 
E)  All are true. 
A)  It is not highly specific and will catalyze phosphorylation of a number of hexoses at the six position. 
B)  Hexoses bind the active site and induce a solvent inaccessible fit to the hexose. 
C)  Glycerol may fit into the active site, but it does not bind to induce a conformational change necessary for catalysis. 
D)  When a hexose binds the active site, the active site is modified to promote changes in the substrate to a transitional-state intermediate. 
E)  All are true.

Question 2

The free energy of activation, ΔG   , is defined as:

Accepted Answer

A)  The average free energy of the product formed. 
B)  The rate of a chemical reaction in relationship to the concentration of reactant molecules. 
C)  The energy required to raise the average energy of one mole of reactant to the transition state energy. 
D)  The amount of energy released by a spontaneous reaction. 
E)  The lowest point on a free energy diagram. 
A)  The average free energy of the product formed. 
B)  The rate of a chemical reaction in relationship to the concentration of reactant molecules. 
C)  The energy required to raise the average energy of one mole of reactant to the transition state energy. 
D)  The amount of energy released by a spontaneous reaction. 
E)  The lowest point on a free energy diagram.

Question 3

Which statement is correct about the Michaelis-Menten constant, Km, for the kinetic mechanism below?

Accepted Answer

A)  It is numerically equal to the substrate concentration required to achieve one half the maximum velocity. 
B)  Its defined as Km = k1/(k−1 + k2). 
C)  It is approximately equal to the dissociation constant for the enzyme-substrate complex to E + P. 
D)  The value of Km is constant for an enzyme regardless of the specific substrate molecule used to determine it. 
E)  Its numeric value has the units of moles−1. 
A)  It is numerically equal to the substrate concentration required to achieve one half the maximum velocity. 
B)  Its defined as Km = k1/(k−1 + k2). 
C)  It is approximately equal to the dissociation constant for the enzyme-substrate complex to E + P. 
D)  The value of Km is constant for an enzyme regardless of the specific substrate molecule used to determine it. 
E)  Its numeric value has the units of moles−1.

Question 4

In the reaction mechanism below, ____ are competitive for binding to free enzyme E.

Accepted Answer

A)  P and A 
B)  A and B 
C)  B and Q 
D)  Q and A 
E)  All of the above 
A)  P and A 
B)  A and B 
C)  B and Q 
D)  Q and A 
E)  All of the above

Question 5

For an enzyme-catalyzed reaction, the initial velocity was determined at two different concentrations of the substrate. Which of the following would be closest to the value of VS1U1B1maxS1U1B0?

Accepted Answer

A)  4.7 mM/min 
B)  0.67 mM/min 
C)  3.19 mM/min 
D)  1.5 mM/min 
E)  0.32 mM/min 
A)  4.7 mM/min 
B)  0.67 mM/min 
C)  3.19 mM/min 
D)  1.5 mM/min 
E)  0.32 mM/min

Question 6

Identify the type of reaction that would give the following graph:

Accepted Answer

A)  double displacement bisubstrate reaction. 
B)  competitively inhibited reaction. 
C)  single displacement bisubstrate reaction. 
D)  mixed noncompetitively inhibited reaction. 
E)  pure noncompetitively inhibited reaction. 
A)  double displacement bisubstrate reaction. 
B)  competitively inhibited reaction. 
C)  single displacement bisubstrate reaction. 
D)  mixed noncompetitively inhibited reaction. 
E)  pure noncompetitively inhibited reaction.

Question 7

If an enzyme has a Vmax of 15 mM/min, what is the velocity if the substrate is present at 1/5 of the Km?

Accepted Answer

A)  12 mM/min 
B)  6 mM/min 
C)  3 mM/min 
D)  2.5 mM/min 
E)  cannot be determined from given information 
A)  12 mM/min 
B)  6 mM/min 
C)  3 mM/min 
D)  2.5 mM/min 
E)  cannot be determined from given information

Question 8

What reaction would NOT proceed via bimolecular elementary steps?

Accepted Answer

A)  C + D → T + U 
B)  A reaction with a rate constant in the units of s−1. 
C)  2A → D + E 
D)  A reaction with a molecularity of 2. 
E)  A reaction with a rate constant in the units of M−1s−1. 
A)  C + D → T + U 
B)  A reaction with a rate constant in the units of s−1. 
C)  2A → D + E 
D)  A reaction with a molecularity of 2. 
E)  A reaction with a rate constant in the units of M−1s−1.

Question 9

Discuss the induced fit model that explains enzyme specificity.​

Accepted Answer

Realization of the conformational flexib

Question 10

All are distinctive features of enzymes EXCEPT:

Accepted Answer

A)  regulation. 
B)  catalytic activity. 
C)  ability to change ΔG. 
D)  specificity. 
E)  none is true. 
A)  regulation. 
B)  catalytic activity. 
C)  ability to change ΔG. 
D)  specificity. 
E)  none is true.

Question 11

Explain the mechanism of action of penicillin as an example of irreversible inhibition.​

Accepted Answer

The antibiotic penicillin exerts its eff

Question 12

All of the following statements about competitive inhibition are correct EXCEPT:

Accepted Answer

A)  Competitive inhibitors are often chemical analogs of the substrate. 
B)  For a group-specific enzyme, one substrate would be a competitive inhibitor of reactions of the other possible substrate. 
C)  Sometimes a product of an enzyme-catalyzed reaction is a competitive inhibitor of its own production. 
D)  In the presence of a competitive inhibitor, the apparent Km would be altered and Vmax would be decreased. 
E)  Competitive inhibitors usually interact with the enzyme at the binding site for a substrate. 
A)  Competitive inhibitors are often chemical analogs of the substrate. 
B)  For a group-specific enzyme, one substrate would be a competitive inhibitor of reactions of the other possible substrate. 
C)  Sometimes a product of an enzyme-catalyzed reaction is a competitive inhibitor of its own production. 
D)  In the presence of a competitive inhibitor, the apparent Km would be altered and Vmax would be decreased. 
E)  Competitive inhibitors usually interact with the enzyme at the binding site for a substrate.

Question 13

Which of the following statements regarding inhibitors is correct?

Accepted Answer

A)  a transition state analog binds covalently to the enzyme 
B)  a non-competitive inhibitor causes an increase in the Vmax 
C)  the presence of a competitive inhibitor can be overcome by addition of more inhibitor 
D)  a competitive inhibitor results in a higher apparent Km value 
E)  none of the above are correct 
A)  a transition state analog binds covalently to the enzyme 
B)  a non-competitive inhibitor causes an increase in the Vmax 
C)  the presence of a competitive inhibitor can be overcome by addition of more inhibitor 
D)  a competitive inhibitor results in a higher apparent Km value 
E)  none of the above are correct

Question 14

In the glutamate:aspartate aminotransferase catalyzed reaction mechanism, glutamate would react with ____ to form α-ketoglutarate.

Accepted Answer

A)  E-pyridoxal phosphate complex 
B)  E-pyridoxamine phosphate complex 
C)  aspartate 
D)  oxaloacetate 
E)  none of the above 
A)  E-pyridoxal phosphate complex 
B)  E-pyridoxamine phosphate complex 
C)  aspartate 
D)  oxaloacetate 
E)  none of the above

Question 15

Which of the following statements is NOT characteristic of kcat/Km?

Accepted Answer

A)  It corresponds to a second-order rate constant. 
B)  It provides an excellent parameter for comparison of the catalytic efficiency of enzymes. 
C)  It reflects the property of the enzyme when substrate concentration is at saturation. 
D)  The upper limit for the kcat/Km value is fixed by the diffusion-controlled limit for reactions, which is 109 M−1 s−1. 
E)  It is also referred to as the turnover number. 
A)  It corresponds to a second-order rate constant. 
B)  It provides an excellent parameter for comparison of the catalytic efficiency of enzymes. 
C)  It reflects the property of the enzyme when substrate concentration is at saturation. 
D)  The upper limit for the kcat/Km value is fixed by the diffusion-controlled limit for reactions, which is 109 M−1 s−1. 
E)  It is also referred to as the turnover number.

Question 16

When every enzyme molecule in the reaction mixture has its substrate-binding site occupied by substrate, the kinetics become ____-order, and the velocity is ____.

Accepted Answer

A)  zero; Vmax 
B)  first; Vmax 
C)  second; Vmax/2 
D)  zero; Vmax/2 
E)  first; Vmax/2 
A)  zero; Vmax 
B)  first; Vmax 
C)  second; Vmax/2 
D)  zero; Vmax/2 
E)  first; Vmax/2

Question 17

Malonate inhibition of succinate dehydrogenase is an example of:

Accepted Answer

A)  noncompetitive inhibition. 
B)  competitive inhibition. 
C)  mixed noncompetitive inhibition. 
D)  irreversible inhibition. 
E)  uncompetitive inhibition. 
A)  noncompetitive inhibition. 
B)  competitive inhibition. 
C)  mixed noncompetitive inhibition. 
D)  irreversible inhibition. 
E)  uncompetitive inhibition.

Question 18

Sildenafil citrate (Viagra) was developed as an inhibitor of:

Accepted Answer

A)  acid phosphatases. 
B)  cAMP phosphodiesterases. 
C)  glycogen phosphorylase. 
D)  cGMP phosphodiesterases. 
E)  testosterone reductase. 
A)  acid phosphatases. 
B)  cAMP phosphodiesterases. 
C)  glycogen phosphorylase. 
D)  cGMP phosphodiesterases. 
E)  testosterone reductase.

Question 19

All of the following are true statements about the transition state of a reaction EXCEPT:

Accepted Answer

A)  The transition state is not an appropriate indication of the rate of a reaction. 
B)  The transition state is located at the height of a free energy diagram. 
C)  The energy required to raise the average energy of one mole of reactant to the transition state is the free energy of activation. 
D)  Reaching the transition state indicates that there is a high probability that the reaction will occur. 
E)  The transition state energy level is the sum of the energy levels of the reactants and products. 
A)  The transition state is not an appropriate indication of the rate of a reaction. 
B)  The transition state is located at the height of a free energy diagram. 
C)  The energy required to raise the average energy of one mole of reactant to the transition state is the free energy of activation. 
D)  Reaching the transition state indicates that there is a high probability that the reaction will occur. 
E)  The transition state energy level is the sum of the energy levels of the reactants and products.

Question 20

Catalytic antibodies, also called ____, are generated against an antigen that is:

Accepted Answer

A)  abzymes; an analog of the transition-state intermediate in the reaction. 
B)  abzymes; the substrate of the reaction. 
C)  zymogens; an analog of the product of the reaction. 
D)  holoenzyme; an analog of the transition-state intermediate in the reaction. 
E)  none of the above. 
A)  abzymes; an analog of the transition-state intermediate in the reaction. 
B)  abzymes; the substrate of the reaction. 
C)  zymogens; an analog of the product of the reaction. 
D)  holoenzyme; an analog of the transition-state intermediate in the reaction. 
E)  none of the above.

Exam 13: Enzymeskinetics and Specificity

All are characteristics of the enzyme hexokinase EXCEPT:

The free energy of activation, ΔG , is defined as:

Which statement is correct about the Michaelis-Menten constant, Km, for the kinetic mechanism below?

In the reaction mechanism below, ____ are competitive for binding to free enzyme E.

For an enzyme-catalyzed reaction, the initial velocity was determined at two different concentrations of the substrate. Which of the following would be closest to the value of Vmax?

Identify the type of reaction that would give the following graph:

If an enzyme has a Vmax of 15 mM/min, what is the velocity if the substrate is present at 1/5 of the Km?

What reaction would NOT proceed via bimolecular elementary steps?

Discuss the induced fit model that explains enzyme specificity.​

All are distinctive features of enzymes EXCEPT:

Explain the mechanism of action of penicillin as an example of irreversible inhibition.​

All of the following statements about competitive inhibition are correct EXCEPT:

Which of the following statements regarding inhibitors is correct?

In the glutamate:aspartate aminotransferase catalyzed reaction mechanism, glutamate would react with ____ to form α-ketoglutarate.

Which of the following statements is NOT characteristic of kcat/Km?

When every enzyme molecule in the reaction mixture has its substrate-binding site occupied by substrate, the kinetics become ____-order, and the velocity is ____.

Malonate inhibition of succinate dehydrogenase is an example of:

Sildenafil citrate (Viagra) was developed as an inhibitor of:

All of the following are true statements about the transition state of a reaction EXCEPT:

Catalytic antibodies, also called ____, are generated against an antigen that is:

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

Water: the Medium of Life

Thermodynamics of Biological Systems

Amino Acids and the Peptide Bond

Proteins: Their Primary Structure and Biological Functions

Proteins: Secondary, Tertiary, and Quaternary Structure

Carbohydrates and the Glycoconjugates of Cell Surfaces

Lipids

Membranes and Membrane Transport

Nucleotides and Nucleic Acids

Structure of Nucleic Acids

Recombinant Dna, Cloning, Chimeric Genes, and Synthetic Biology

Mechanisms of Enzyme Action

Enzyme Regulation

Molecular Motors

Metabolism: an Overview

Glycolysis

The Tricarboxylic Acid Cycle

Electron Transport and Oxidative Phosphorylation

Photosynthesis

Gluconeogenesis, Glycogen Metabolism, and the Pentose Phosphate Pathway

Fatty Acid Catabolism

Lipid Biosynthesis

Nitrogen Acquisition and Amino Acid Metabolism

Synthesis and Degradation of Nucleotides

Metabolic Integration and Organ Specialization

Dna Metabolism: Replication, Recombination, and Repair

Transcription and the Regulation of Gene Expression

Protein Synthesis

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

The Reception and Transmission of Extracellular Information

Filters

Which statement is correct about the Michaelis-Menten constant, K_m, for the kinetic mechanism below?

For an enzyme-catalyzed reaction, the initial velocity was determined at two different concentrations of the substrate. Which of the following would be closest to the value of V_max?

If an enzyme has a V_max of 15 mM/min, what is the velocity if the substrate is present at 1/5 of the K_m?

Discuss the induced fit model that explains enzyme specificity.

Explain the mechanism of action of penicillin as an example of irreversible inhibition.

Which of the following statements is NOT characteristic of k_cat/K_m?

When every enzyme molecule in the reaction mixture has its substrate-binding site occupied by substrate, the kinetics become -order, and the velocity is .