CHEM 210 Module 6 Exam ()
(PDF) | Biochemistry | Geneva College
CHEM 210 Module 6 Exam () | Biochemistry | Geneva College
Examination Overview
This examination assesses student mastery of Module 6 content in CHEM 210 Biochemistry at
Geneva College. The scope encompasses enzyme kinetics, catalytic mechanisms, inhibition, and
regulation—core topics that bridge foundational biochemistry with advanced metabolic
understanding. Questions are distributed across enzyme classification and cofactors, Michaelis-
Menten kinetics, Lineweaver-Burk analysis, multisubstrate reactions, catalytic mechanisms (acid-
base, covalent, metal-ion), reversible and irreversible inhibition, allosteric regulation, and covalent
modification of enzymes. The examination includes foundational knowledge items, application-
based problems, and analytical scenarios requiring interpretation of kinetic data.
Table of Contents
1. Enzyme Fundamentals and Classification (Q1–Q20)
2. Cofactors and Coenzymes (Q21–Q40)
3. Michaelis-Menten Kinetics (Q41–Q70)
4. Lineweaver-Burk and Kinetic Analysis (Q71–Q95)
5. Multisubstrate Reactions and Bisubstrate Kinetics (Q96–Q110)
6. Catalytic Mechanisms (Q111–Q135)
7. Enzyme Inhibition (Q136–Q165)
8. Allosteric Regulation (Q166–Q185)
9. Covalent Modification and Zymogens (Q186–Q200)
Questions 1–200
Section 1: Enzyme Fundamentals and Classification (Q1–Q20)
Q1. Which of the following statements best describes the fundamental role of enzymes in
biochemical reactions?
A. Enzymes increase the equilibrium constant of a reaction, favoring product formation.
B. Enzymes lower the activation energy barrier, accelerating the rate at which equilibrium is
achieved.
pg. 1
,C. Enzymes consume ATP to drive thermodynamically unfavorable reactions forward.
D. Enzymes permanently alter the standard free energy change (ΔG°′) of a reaction.
Correct Answer: B. Enzymes lower the activation energy barrier, accelerating the rate at which
equilibrium is achieved.
Rationale: Enzymes are biological catalysts that accelerate reactions by stabilizing the transition
state and reducing the activation energy (ΔG‡). They do not alter the equilibrium constant or the
overall free energy change of a reaction—these are thermodynamic properties determined by the
substrates and products. Option A is incorrect because enzymes do not change equilibrium
constants; they only accelerate the approach to equilibrium. Option C describes active transport or
coupled reactions, not general enzyme function. Option D is incorrect because ΔG°′ is a
thermodynamic constant unaffected by catalysts.
Q2. According to the International Union of Biochemistry and Molecular Biology (IUBMB)
classification system, to which class does an enzyme that catalyzes the transfer of a phosphate group
from ATP to glucose belong?
A. Oxidoreductase
B. Transferase
C. Hydrolase
D. Ligase
Correct Answer: B. Transferase
Rationale: Transferases catalyze the transfer of functional groups (e.g., phosphate, methyl, acyl)
from one molecule to another. Hexokinase, which transfers a phosphoryl group from ATP to glucose,
is a classic example of a transferase (EC 2.7.1.1). Oxidoreductases catalyze oxidation-reduction
reactions. Hydrolases catalyze hydrolytic cleavage of bonds. Ligases catalyze bond formation coupled
to ATP hydrolysis.
Q3. An enzyme that catalyzes the cleavage of a carbon-carbon bond without the addition of water
and without oxidation-reduction is classified as which of the following?
A. Hydrolase
B. Lyase
C. Isomerase
D. Ligase
Correct Answer: B. Lyase
Rationale: Lyases catalyze the non-hydrolytic cleavage of C-C, C-O, C-N, and other bonds, often
generating a double bond or a new ring structure. Aldolase, which cleaves fructose-1,6-bisphosphate
into two triose phosphates, is an example of a lyase. Hydrolases use water to cleave bonds.
Isomerases catalyze intramolecular rearrangements. Ligases form bonds using ATP.
Q4. The active site of an enzyme is best described as:
pg. 2
,A. The entire surface of the enzyme that contacts solvent
B. A three-dimensional pocket or cleft where substrate binds and catalysis occurs
C. The region of the enzyme that binds allosteric regulators exclusively
D. The portion of the enzyme removed during zymogen activation
Correct Answer: B. A three-dimensional pocket or cleft where substrate binds and catalysis occurs
Rationale: The active site is a specific three-dimensional region, typically a pocket or cleft, formed by
amino acid residues from different parts of the polypeptide chain (and sometimes from different
subunits). It provides a microenvironment optimized for substrate binding and catalysis. Option A is
too broad; not all surface contacts are catalytic. Option C describes allosteric sites, which are distinct
from active sites. Option D describes activation peptides, not active sites.
Q5. Which of the following is a characteristic feature of enzyme active sites that contributes directly
to catalytic efficiency?
A. The active site typically binds substrate with extremely high affinity (Kd in the picomolar range).
B. The active site is usually rigid and complementary to the substrate's ground-state structure.
C. The active site often excludes water and provides a low-dielectric environment.
D. The active site contains only amino acid side chains and never metal ions or cofactors.
Correct Answer: C. The active site often excludes water and provides a low-dielectric environment.
Rationale: Exclusion of bulk water from the active site enhances electrostatic interactions between
enzyme and substrate, strengthens hydrogen bonding, and prevents competing hydrolysis reactions.
Option A is incorrect: enzymes bind substrates with modest affinity (Kd often in the micromolar to
millimolar range), which allows product release. Option B is incorrect because active sites are often
flexible and complementary to the transition state, not the ground state (induced fit). Option D is
incorrect because many enzymes require metal ions or organic cofactors at their active sites.
Q6. The "induced fit" model of enzyme-substrate binding proposes that:
A. The substrate changes conformation to fit a rigid active site.
B. The enzyme undergoes a conformational change upon substrate binding that aligns catalytic
groups.
C. The active site is pre-formed in a complementary shape to the substrate.
D. Substrate binding occurs only after allosteric activation.
Correct Answer: B. The enzyme undergoes a conformational change upon substrate binding that
aligns catalytic groups.
Rationale: The induced fit model, proposed by Daniel Koshland, posits that the active site is not
rigidly pre-formed but undergoes conformational changes upon substrate binding. This
conformational change brings catalytic residues into proper orientation and often stabilizes the
transition state. Option A describes the outdated "lock-and-key" model in reverse. Option C
describes the lock-and-key model. Option D describes allosteric regulation, not general substrate
binding.
pg. 3
, Q7. Which of the following enzymes would be classified as an oxidoreductase?
A. Carbonic anhydrase (catalyzes CO₂ hydration)
B. Alcohol dehydrogenase (catalyzes ethanol to acetaldehyde)
C. Phosphoglucomutase (catalyzes glucose-1-P to glucose-6-P)
D. Aspartate transcarbamoylase (catalyzes carbamoyl phosphate + aspartate)
Correct Answer: B. Alcohol dehydrogenase (catalyzes ethanol to acetaldehyde)
Rationale: Oxidoreductases catalyze oxidation-reduction reactions, typically involving NAD+ or
NADP+ as electron acceptors. Alcohol dehydrogenase transfers hydride from ethanol to NAD+,
producing acetaldehyde and NADH, making it an oxidoreductase. Carbonic anhydrase is a lyase.
Phosphoglucomutase is an isomerase. Aspartate transcarbamoylase is a transferase.
Q8. The turnover number (kcat) of an enzyme represents:
A. The number of substrate molecules converted to product per enzyme molecule per unit time at
saturating substrate
B. The substrate concentration at which the reaction rate is half-maximal
C. The rate constant for the dissociation of the enzyme-substrate complex
D. The efficiency of substrate binding in the absence of catalysis
Correct Answer: A. The number of substrate molecules converted to product per enzyme molecule
per unit time at saturating substrate
Rationale: kcat (also called turnover number) is the catalytic constant representing the maximum
number of substrate molecules converted to product per active site per unit time when the enzyme
is fully saturated with substrate. Option B defines KM. Option C defines koff. Option D describes
binding affinity, not catalytic rate.
Q9. For a typical enzyme, the catalytic efficiency is best expressed as:
A. kcat alone
B. KM alone
C. kcat/KM
D. Vmax alone
Correct Answer: C. kcat/KM
Rationale: The ratio kcat/KM is the apparent second-order rate constant for the reaction of enzyme
and substrate at low substrate concentrations. It accounts for both binding (KM) and catalysis (kcat),
providing a measure of catalytic efficiency. The diffusion-controlled limit for kcat/KM is
approximately 10⁸ to 10⁹ M⁻¹s⁻¹, representing the maximum possible efficiency. Neither kcat, KM,
nor Vmax alone adequately captures overall efficiency.
Q10. Which of the following statements about enzyme specificity is most accurate?
A. Most enzymes can catalyze reactions with a wide range of structurally unrelated substrates.
B. Enzyme specificity is determined primarily by the amino acid sequence at the active site and the
pg. 4
(PDF) | Biochemistry | Geneva College
CHEM 210 Module 6 Exam () | Biochemistry | Geneva College
Examination Overview
This examination assesses student mastery of Module 6 content in CHEM 210 Biochemistry at
Geneva College. The scope encompasses enzyme kinetics, catalytic mechanisms, inhibition, and
regulation—core topics that bridge foundational biochemistry with advanced metabolic
understanding. Questions are distributed across enzyme classification and cofactors, Michaelis-
Menten kinetics, Lineweaver-Burk analysis, multisubstrate reactions, catalytic mechanisms (acid-
base, covalent, metal-ion), reversible and irreversible inhibition, allosteric regulation, and covalent
modification of enzymes. The examination includes foundational knowledge items, application-
based problems, and analytical scenarios requiring interpretation of kinetic data.
Table of Contents
1. Enzyme Fundamentals and Classification (Q1–Q20)
2. Cofactors and Coenzymes (Q21–Q40)
3. Michaelis-Menten Kinetics (Q41–Q70)
4. Lineweaver-Burk and Kinetic Analysis (Q71–Q95)
5. Multisubstrate Reactions and Bisubstrate Kinetics (Q96–Q110)
6. Catalytic Mechanisms (Q111–Q135)
7. Enzyme Inhibition (Q136–Q165)
8. Allosteric Regulation (Q166–Q185)
9. Covalent Modification and Zymogens (Q186–Q200)
Questions 1–200
Section 1: Enzyme Fundamentals and Classification (Q1–Q20)
Q1. Which of the following statements best describes the fundamental role of enzymes in
biochemical reactions?
A. Enzymes increase the equilibrium constant of a reaction, favoring product formation.
B. Enzymes lower the activation energy barrier, accelerating the rate at which equilibrium is
achieved.
pg. 1
,C. Enzymes consume ATP to drive thermodynamically unfavorable reactions forward.
D. Enzymes permanently alter the standard free energy change (ΔG°′) of a reaction.
Correct Answer: B. Enzymes lower the activation energy barrier, accelerating the rate at which
equilibrium is achieved.
Rationale: Enzymes are biological catalysts that accelerate reactions by stabilizing the transition
state and reducing the activation energy (ΔG‡). They do not alter the equilibrium constant or the
overall free energy change of a reaction—these are thermodynamic properties determined by the
substrates and products. Option A is incorrect because enzymes do not change equilibrium
constants; they only accelerate the approach to equilibrium. Option C describes active transport or
coupled reactions, not general enzyme function. Option D is incorrect because ΔG°′ is a
thermodynamic constant unaffected by catalysts.
Q2. According to the International Union of Biochemistry and Molecular Biology (IUBMB)
classification system, to which class does an enzyme that catalyzes the transfer of a phosphate group
from ATP to glucose belong?
A. Oxidoreductase
B. Transferase
C. Hydrolase
D. Ligase
Correct Answer: B. Transferase
Rationale: Transferases catalyze the transfer of functional groups (e.g., phosphate, methyl, acyl)
from one molecule to another. Hexokinase, which transfers a phosphoryl group from ATP to glucose,
is a classic example of a transferase (EC 2.7.1.1). Oxidoreductases catalyze oxidation-reduction
reactions. Hydrolases catalyze hydrolytic cleavage of bonds. Ligases catalyze bond formation coupled
to ATP hydrolysis.
Q3. An enzyme that catalyzes the cleavage of a carbon-carbon bond without the addition of water
and without oxidation-reduction is classified as which of the following?
A. Hydrolase
B. Lyase
C. Isomerase
D. Ligase
Correct Answer: B. Lyase
Rationale: Lyases catalyze the non-hydrolytic cleavage of C-C, C-O, C-N, and other bonds, often
generating a double bond or a new ring structure. Aldolase, which cleaves fructose-1,6-bisphosphate
into two triose phosphates, is an example of a lyase. Hydrolases use water to cleave bonds.
Isomerases catalyze intramolecular rearrangements. Ligases form bonds using ATP.
Q4. The active site of an enzyme is best described as:
pg. 2
,A. The entire surface of the enzyme that contacts solvent
B. A three-dimensional pocket or cleft where substrate binds and catalysis occurs
C. The region of the enzyme that binds allosteric regulators exclusively
D. The portion of the enzyme removed during zymogen activation
Correct Answer: B. A three-dimensional pocket or cleft where substrate binds and catalysis occurs
Rationale: The active site is a specific three-dimensional region, typically a pocket or cleft, formed by
amino acid residues from different parts of the polypeptide chain (and sometimes from different
subunits). It provides a microenvironment optimized for substrate binding and catalysis. Option A is
too broad; not all surface contacts are catalytic. Option C describes allosteric sites, which are distinct
from active sites. Option D describes activation peptides, not active sites.
Q5. Which of the following is a characteristic feature of enzyme active sites that contributes directly
to catalytic efficiency?
A. The active site typically binds substrate with extremely high affinity (Kd in the picomolar range).
B. The active site is usually rigid and complementary to the substrate's ground-state structure.
C. The active site often excludes water and provides a low-dielectric environment.
D. The active site contains only amino acid side chains and never metal ions or cofactors.
Correct Answer: C. The active site often excludes water and provides a low-dielectric environment.
Rationale: Exclusion of bulk water from the active site enhances electrostatic interactions between
enzyme and substrate, strengthens hydrogen bonding, and prevents competing hydrolysis reactions.
Option A is incorrect: enzymes bind substrates with modest affinity (Kd often in the micromolar to
millimolar range), which allows product release. Option B is incorrect because active sites are often
flexible and complementary to the transition state, not the ground state (induced fit). Option D is
incorrect because many enzymes require metal ions or organic cofactors at their active sites.
Q6. The "induced fit" model of enzyme-substrate binding proposes that:
A. The substrate changes conformation to fit a rigid active site.
B. The enzyme undergoes a conformational change upon substrate binding that aligns catalytic
groups.
C. The active site is pre-formed in a complementary shape to the substrate.
D. Substrate binding occurs only after allosteric activation.
Correct Answer: B. The enzyme undergoes a conformational change upon substrate binding that
aligns catalytic groups.
Rationale: The induced fit model, proposed by Daniel Koshland, posits that the active site is not
rigidly pre-formed but undergoes conformational changes upon substrate binding. This
conformational change brings catalytic residues into proper orientation and often stabilizes the
transition state. Option A describes the outdated "lock-and-key" model in reverse. Option C
describes the lock-and-key model. Option D describes allosteric regulation, not general substrate
binding.
pg. 3
, Q7. Which of the following enzymes would be classified as an oxidoreductase?
A. Carbonic anhydrase (catalyzes CO₂ hydration)
B. Alcohol dehydrogenase (catalyzes ethanol to acetaldehyde)
C. Phosphoglucomutase (catalyzes glucose-1-P to glucose-6-P)
D. Aspartate transcarbamoylase (catalyzes carbamoyl phosphate + aspartate)
Correct Answer: B. Alcohol dehydrogenase (catalyzes ethanol to acetaldehyde)
Rationale: Oxidoreductases catalyze oxidation-reduction reactions, typically involving NAD+ or
NADP+ as electron acceptors. Alcohol dehydrogenase transfers hydride from ethanol to NAD+,
producing acetaldehyde and NADH, making it an oxidoreductase. Carbonic anhydrase is a lyase.
Phosphoglucomutase is an isomerase. Aspartate transcarbamoylase is a transferase.
Q8. The turnover number (kcat) of an enzyme represents:
A. The number of substrate molecules converted to product per enzyme molecule per unit time at
saturating substrate
B. The substrate concentration at which the reaction rate is half-maximal
C. The rate constant for the dissociation of the enzyme-substrate complex
D. The efficiency of substrate binding in the absence of catalysis
Correct Answer: A. The number of substrate molecules converted to product per enzyme molecule
per unit time at saturating substrate
Rationale: kcat (also called turnover number) is the catalytic constant representing the maximum
number of substrate molecules converted to product per active site per unit time when the enzyme
is fully saturated with substrate. Option B defines KM. Option C defines koff. Option D describes
binding affinity, not catalytic rate.
Q9. For a typical enzyme, the catalytic efficiency is best expressed as:
A. kcat alone
B. KM alone
C. kcat/KM
D. Vmax alone
Correct Answer: C. kcat/KM
Rationale: The ratio kcat/KM is the apparent second-order rate constant for the reaction of enzyme
and substrate at low substrate concentrations. It accounts for both binding (KM) and catalysis (kcat),
providing a measure of catalytic efficiency. The diffusion-controlled limit for kcat/KM is
approximately 10⁸ to 10⁹ M⁻¹s⁻¹, representing the maximum possible efficiency. Neither kcat, KM,
nor Vmax alone adequately captures overall efficiency.
Q10. Which of the following statements about enzyme specificity is most accurate?
A. Most enzymes can catalyze reactions with a wide range of structurally unrelated substrates.
B. Enzyme specificity is determined primarily by the amino acid sequence at the active site and the
pg. 4
