Question 1

An enzymatic reaction has a Vmax of 30 μM/min and a Km of 50 μM. If the concentration of the substrate is 25 μM, which of the following is true?

Accepted Answer

A)  the velocity will be 7.5 μM/min 
B)  the velocity will be 20 μM/min 
C)  the velocity will be 10 μM/min 
D)  the velocity will be 25 μM/min 
E)  the velocity will be 15 μM/min 
A)  the velocity will be 7.5 μM/min 
B)  the velocity will be 20 μM/min 
C)  the velocity will be 10 μM/min 
D)  the velocity will be 25 μM/min 
E)  the velocity will be 15 μM/min B

Question 2

Which of the following is true regarding the Briggs and Haldane steady state assumption?

Accepted Answer

A)  It is defined by the equation
  
B)  It states the rate of enzyme-substrate complex formation differs from the rate of enzyme-substrate disappearance. 
C)  The concentration of the enzyme-substrate complex reaches a constant value even in a dynamic system. 
D)  The enzyme-substrate complex will always dissociate to form E + P. 
E)  The total amount of enzyme is variable, depending on the amount of substrate available. 
A)  It is defined by the equation
  
B)  It states the rate of enzyme-substrate complex formation differs from the rate of enzyme-substrate disappearance. 
C)  The concentration of the enzyme-substrate complex reaches a constant value even in a dynamic system. 
D)  The enzyme-substrate complex will always dissociate to form E + P. 
E)  The total amount of enzyme is variable, depending on the amount of substrate available. C

Question 3

Carbonic anhydrase has two substrates, carbon dioxide and bicarbonate, which are both converted to carbonic acid. Kinetic data for each is given below. While determining the kinetics of HCO3- as a substrate, how would the addition of CO2 effect the reaction if the rate were measured by the disappearance of bicarbonate?
Substrate
Km (mM)
Kcat (sec-1)
Kcat/Km (m M-1sec-1)
CO2
HCO3-
12
26
1×106
4×105
8)3×104
1.5×104

Accepted Answer

A)  CO2 would increase the activity of the enzyme 
B)  CO2 would cause an apparent decrease in the Km for HCO3- 
C)  CO2 would act as a noncompetitive inhibitor 
D)  CO2 would act as a competitive inhibitor 
E)  none of the above 
A)  CO2 would increase the activity of the enzyme 
B)  CO2 would cause an apparent decrease in the Km for HCO3- 
C)  CO2 would act as a noncompetitive inhibitor 
D)  CO2 would act as a competitive inhibitor 
E)  none of the above D

Question 4

All are true for inhibitor I if it is a competitive inhibitor EXCEPT:

Accepted Answer

A)  It binds a site other than the active site. 
B)  It is structurally similar to the substrate. 
C)  EI does not give rise to E + P. 
D)  For a given [I], v decreases. 
E)  At some point, S can displace all of I on E. 
A)  It binds a site other than the active site. 
B)  It is structurally similar to the substrate. 
C)  EI does not give rise to E + P. 
D)  For a given [I], v decreases. 
E)  At some point, S can displace all of I on E.

Question 5

Discuss the effect of substrate concentration, [S], on the rate of a reaction, v.​

Accepted Answer

At low concentrations of the substrate S

Question 6

In transforming the Michaelis-Menten equation into a straight line equation, y = mx + b, the Lineweaver-Burk double reciprocal plot, which of the following is NOT a true representation?

Accepted Answer

A)  slope = Km/Vmax 
B)  y-intercept is 1/Vmax 
C)  x-intercept is 1/Km 
D)  y = 1/V 
E)  x = 1/[S] 
A)  slope = Km/Vmax 
B)  y-intercept is 1/Vmax 
C)  x-intercept is 1/Km 
D)  y = 1/V 
E)  x = 1/[S]

Question 7

Penicillin and other β-lactam antibiotics form a covalent bond to the enzyme glycoprotein transpeptidase. What type of bond is formed?

Accepted Answer

A)  ester 
B)  thioester 
C)  amide 
D)  phosphate 
E)  none of the above 
A)  ester 
B)  thioester 
C)  amide 
D)  phosphate 
E)  none of the above

Question 8

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 Km?
[S] (mM)
Vo(mM/min)
1)0
2)0
4)0
2)8

Accepted Answer

A)  0.17 mM 
B)  5.7 mM 
C)  2.7 mM 
D)  0.60 mM 
E)  1.7 mM 
A)  0.17 mM 
B)  5.7 mM 
C)  2.7 mM 
D)  0.60 mM 
E)  1.7 mM

Question 9

The specific site on the enzyme where ____ binds and catalysis occurs is called the ____ site.

Accepted Answer

A)  coenzyme; substrate 
B)  substrate; active 
C)  coenzyme; regulatory 
D)  regulatory; active 
E)  none of the above 
A)  coenzyme; substrate 
B)  substrate; active 
C)  coenzyme; regulatory 
D)  regulatory; active 
E)  none of the above

Question 10

All are true for catalysts EXCEPT:

Accepted Answer

A)  They work by lowering the energy of activation. 
B)  The average energy of the reaction is unchanged. 
C)  They combine transiently with the reactants promoting a reactive transition state condition. 
D)  They are regenerated after each reaction cycle. 
E)  All are true. 
A)  They work by lowering the energy of activation. 
B)  The average energy of the reaction is unchanged. 
C)  They combine transiently with the reactants promoting a reactive transition state condition. 
D)  They are regenerated after each reaction cycle. 
E)  All are true.

Question 11

If the rate constant for the enzyme catalyzed reaction is 2 × 105/sec and the rate constant for the uncatalyzed reaction is 2 × 10−6/sec, the catalytic power of the enzyme is:

Accepted Answer

A)  1011 
B)  2 × 10−11 
C)  10−11 
D)  10−1 
E)  2 × 10−1 
A)  1011 
B)  2 × 10−11 
C)  10−11 
D)  10−1 
E)  2 × 10−1

Question 12

In uncompetitive inhibition:

Accepted Answer

A)  I combines only with ES. 
B)  I combines only with E. 
C)  I combines with E and ES. 
D)  I combines with EP. 
E)  none of the above. 
A)  I combines only with ES. 
B)  I combines only with E. 
C)  I combines with E and ES. 
D)  I combines with EP. 
E)  none of the above.

Question 13

An enzyme's specificity can be due to:

Accepted Answer

A)  the ratio of catalyzed rate to the uncatalyzed rate of reaction. 
B)  molecular recognition based on structural complementarity. 
C)  amount of enzyme produced by the cell. 
D)  amount of substrate available. 
E)  metabolic activators. 
A)  the ratio of catalyzed rate to the uncatalyzed rate of reaction. 
B)  molecular recognition based on structural complementarity. 
C)  amount of enzyme produced by the cell. 
D)  amount of substrate available. 
E)  metabolic activators.

Question 14

Explain bimolecular reactions.​

Accepted Answer

Consider the complex reaction, where two

Question 15

All of the following are properties of a coenzyme EXCEPT:

Accepted Answer

A)  They are usually actively involved in the catalytic reaction of the enzyme. 
B)  They tend to be stable to heat. 
C)  They can serve as intermediate carriers of functional groups. 
D)  They are protein components. 
E)  They may contain vitamins as part of their structure. 
A)  They are usually actively involved in the catalytic reaction of the enzyme. 
B)  They tend to be stable to heat. 
C)  They can serve as intermediate carriers of functional groups. 
D)  They are protein components. 
E)  They may contain vitamins as part of their structure.

Question 16

How do catalysts work to accelerate a chemical reaction?

Accepted Answer

A)  They raise the average energy of the reactants. 
B)  They provide a means of acceleration by being completely consumed in the reaction. 
C)  They lower the energy of activation. 
D)  They lower the overall free energy change of the reaction. 
E)  They raise the overall free energy change of the reaction. 
A)  They raise the average energy of the reactants. 
B)  They provide a means of acceleration by being completely consumed in the reaction. 
C)  They lower the energy of activation. 
D)  They lower the overall free energy change of the reaction. 
E)  They raise the overall free energy change of the reaction.

Question 17

A plot of 1/V vs. 1/[S] for an enzyme catalyzed reaction gave a line with an equation of y = 0.5x + 0.2. The same enzyme with an inhibitor present gave a line with an equation of y = 1.1x + 0.2. Which of the following statements is true?

Accepted Answer

A)  the type of inhibition is competitive 
B)  the type of inhibition is noncompetitive 
C)  the type of inhibition is uncompetitive 
D)  the Vmax with the inhibitor present has decreased 
E)  the Km with the inhibitor present has decreased 
A)  the type of inhibition is competitive 
B)  the type of inhibition is noncompetitive 
C)  the type of inhibition is uncompetitive 
D)  the Vmax with the inhibitor present has decreased 
E)  the Km with the inhibitor present has decreased

Question 18

In the enzyme catalyzed reaction sequence below, can the E-PO4− intermediate be predicted and why?

Accepted Answer

A)  Yes, the mechanism is a double-displacement reaction. 
B)  Yes, the reaction fits the ping-pong model. 
C)  No, the reaction is random single-displacement. 
D)  No, the reaction is double-displacement. 
E)  None of the above. 
A)  Yes, the mechanism is a double-displacement reaction. 
B)  Yes, the reaction fits the ping-pong model. 
C)  No, the reaction is random single-displacement. 
D)  No, the reaction is double-displacement. 
E)  None of the above.

Question 19

All are true for kcat EXCEPT :

Accepted Answer

A)  referred to as the molecular activity of the enzyme. 
B)  called the turnover number of the enzyme. 
C)  measures the maximal catalytic activity or kinetic efficiency of an enzyme. 
D)  defines the number of substrate molecules converted into product/enzyme molecule/unit of time when the enzyme is saturated with substrate. 
E)  all are true. 
A)  referred to as the molecular activity of the enzyme. 
B)  called the turnover number of the enzyme. 
C)  measures the maximal catalytic activity or kinetic efficiency of an enzyme. 
D)  defines the number of substrate molecules converted into product/enzyme molecule/unit of time when the enzyme is saturated with substrate. 
E)  all are true.

Question 20

The International Units of an enzyme are based on the:

Accepted Answer

A)  ratio of enzyme to other proteins. 
B)  micromoles of product formed per minute. 
C)  moles of substrate reacted. 
D)  micromoles of product produced at Vmax/2. 
E)  none of the above. 
A)  ratio of enzyme to other proteins. 
B)  micromoles of product formed per minute. 
C)  moles of substrate reacted. 
D)  micromoles of product produced at Vmax/2. 
E)  none of the above.

Exam 13: Enzymeskinetics and Specificity

An enzymatic reaction has a Vmax of 30 μM/min and a Km of 50 μM. If the concentration of the substrate is 25 μM, which of the following is true?

Which of the following is true regarding the Briggs and Haldane steady state assumption?

All are true for inhibitor I if it is a competitive inhibitor EXCEPT:

Discuss the effect of substrate concentration, [S], on the rate of a reaction, v.​

In transforming the Michaelis-Menten equation into a straight line equation, y = mx + b, the Lineweaver-Burk double reciprocal plot, which of the following is NOT a true representation?

Penicillin and other β-lactam antibiotics form a covalent bond to the enzyme glycoprotein transpeptidase. What type of bond is formed?

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 Km? [S] (mM) Vo(mM/min) 1)0 2)0 4)0 2)8

The specific site on the enzyme where ____ binds and catalysis occurs is called the ____ site.

All are true for catalysts EXCEPT:

If the rate constant for the enzyme catalyzed reaction is 2 × 105/sec and the rate constant for the uncatalyzed reaction is 2 × 10−6/sec, the catalytic power of the enzyme is:

In uncompetitive inhibition:

An enzyme's specificity can be due to:

Explain bimolecular reactions.​

All of the following are properties of a coenzyme EXCEPT:

How do catalysts work to accelerate a chemical reaction?

A plot of 1/V vs. 1/[S] for an enzyme catalyzed reaction gave a line with an equation of y = 0.5x + 0.2. The same enzyme with an inhibitor present gave a line with an equation of y = 1.1x + 0.2. Which of the following statements is true?

In the enzyme catalyzed reaction sequence below, can the E-PO4− intermediate be predicted and why?

All are true for kcat EXCEPT :

The International Units of an enzyme are based on the:

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

An enzymatic reaction has a V_max of 30 μM/min and a K_m of 50 μM. If the concentration of the substrate is 25 μM, which of the following is true?

Discuss the effect of substrate concentration, [S], on the rate of a reaction, v.

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 K_m? [S] (mM) V_o(mM/min) 1)0 2)0 4)0 2)8

The specific site on the enzyme where binds and catalysis occurs is called the site.

If the rate constant for the enzyme catalyzed reaction is 2 × 10⁵/sec and the rate constant for the uncatalyzed reaction is 2 × 10−⁶/sec, the catalytic power of the enzyme is:

Explain bimolecular reactions.

In the enzyme catalyzed reaction sequence below, can the E-PO₄− intermediate be predicted and why?

All are true for k_cat EXCEPT :