BIOL 334 COMPARATIVE BIOCHEMISTRY EXAM QUESTIONS ANSWERED CORRECTLY LATEST UPDATE
2026
Which of the following statements about the nature of enzyme catalysis is correct? - Answers d) An
enzyme greatly accelerates reaction rates by lowering the activation energy of a chemical reaction.
2. Which of the following statements about Michaelis-Menten enzyme kinetics is correct? - Answers
d) Km, the Michaelis constant, reflects the (apparent) affinity the enzyme has for its substrate.
3. Which of the following statements about competitive inhibition of an enzyme-catalyzed reaction is
correct? - Answers c) The enzyme's Vmax remains unchanged in the presence of a competitive
inhibitor. d
4. Which of the following statements about allosteric enzymes is correct? - Answers d) The 'native
form' of an allosteric enzyme can contain non-catalytic subunits.
5. Which of the following statements about competitive inhibition of an enzyme-catalyzed reaction is
correct? - Answers c) Competitive inhibition can be overcome by the addition of large amounts of
substrate to a reaction.
6. Which of the following statements about Michaelis-Menten kinetics are correct? - Answers e) B and
D are correct
b) A low Km values indicates a high affinity of an enzyme for its substrate. c
d) The Km of an enzyme is unchanged when the enzyme's concentration is increased. e
7. Which of the statements regarding enzymes is false? - Answers c) Enzymes shift the equilibrium
position of a chemical reaction in favor of the product(s).
8. When [S] = KM, the velocity of an enzyme catalyzed reaction is: - Answers d) 0.5 x Vmax.
9. β-galactosidase catalyzes the hydrolysis of the disaccharide lactose to yield glucose and galactose.
What other substrate does β-galactosidase require (apart from galactose)? - Answers c) H2O
10. Lactate dehydrogenase from human skeletal muscle and heart provides a good example of: -
Answers a) isozymes
11. The 'thermal kinetic window' corresponds to the temperature range over which an enzyme
displays: - Answers a) the minimal Km value for its substrate(s)
12. Any non-protein component that is absolutely required by an enzyme for it to have catalytic
activity is referred to as a: - Answers d) co-factor
13. In Mixed-Competitive inhibition of enzyme activity... - Answers b) The inhibitor can bind to the
free enzyme or the enzyme-substrate complex.
14. Which of the following statements about allosteric enzymes is false? - Answers c) Allosteric
effectors compete with the substrate for binding sites.
15. Q10 values for most enzymes from homeothermic (warm blooded) animal species are approx. 2.0,
whereas Q10 values for enzymes of many poikilothermic (cold blooded) species are often much less
than 2.0 (and sometimes close to 1.0). How might this help a poikilothermic animal adapt to its
environment? - Answers a) Metabolic processes are not as severely influenced by changes in
environmental temperature
16. Which of the following techniques or approaches has contributed to our understanding of the
structure of a metabolic pathway in a particular species? - Answers e) B and D are both correct
b) 'pulse-chase' radiolabeling studies
d) annotated genome sequence information
17. What domain of life do all known hyperthermophiles belong to? - Answers d) archaea
18. Which of the following statements completes the following sentence incorrectly?
The thermal stability of 'extremozymes' from hyperthermophiles arises from alterations in their
primary structure such that these proteins exhibit ... - Answers a) increased number of cysteine
residues (leading to more disulfide bridges)
19. An enzyme was determined to have a turnover number (kcat) of 10 sec-1. From the following
data, calculate the total amount of enzyme (in μmol) present during these experiments.
Substrate Concentration (mM): 0.1 0.2 0.4 0.6 10 100 Initial reaction velocity (μmol/minute): 67 128
334 476 600 600
Total Amount of Enzyme = - Answers c) 1 μmol
20. The enzyme phosphofructokinase (PFK) requires Mg2+ to catalyze the reaction: Fructose-6-
phosphate + ATP ----> Fructose-1,6-bisphosphate + ADP. In the absence of Mg2+, the enzyme would
be referred to as the PFK... - Answers (A) apoenzyme
, 21. The 'proteome': - Answers (B) is the set of expressed proteins in a specific cell type, at a given
time, under defined conditions.
22. About 100 years ago Lenoir Michaelis and that lovely Canadian icon Maud Menten derived their
MichaelisMenten equation to relate [S] to the initial rate (Vo) of an enzyme-catalyzed reaction. The
correct expression for their equation is: - Answers (A) Vo = (Vmax x [S]) ÷ (Km + [S])
24. Which of these statements about enzymes that display 'positive cooperativity' with respect to
substrate binding is false? - Answers (E) They can never be both 'homotropic' and 'hetrotropic'.
25. Pyridoxal phosphate is required by most transaminase enzymes as a(n) - Answers (D) co-enzyme
For Questions #26 to #30
β-galactosidase catalyzes the hydrolysis of the disaccharide lactose to yield glucose & galactose. The
enzyme purified from E. coli was used in kinetic studies at 37 oC and gave the following results. 26.
What is the minimal lactose concentration that saturates this enzyme? - Answers (A) 0.20 mM
27. In the presence of 2 mM glucose (a competitive inhibitor) the enzyme's affinity for lactose was
reduced by about 4-fold. What is the enzyme's approximate Km for lactose in the presence of 2 mM
glucose - Answers (B) 0.40 mM
28. Estimate the enzyme's turnover number (kcat value) from the above data. - Answers (E) 10 sec-1
29. Estimate the enzyme's catalytic efficiency from the above data. - Answers (C) 100 sec-1 mM-1
30. Which compound is often added to purification and activity assay buffers of oligomeric enzymes
(have quaternary structure) to help stabilize these enzymes in vitro? - Answers (A) glycerol
31. The maximum optimal growth temperature limit for life (= living & growing cells) is currently
believed to be about: - Answers (B) 125 oC
32. Which of the following is unlikely to be a possible reason for the pH dependence of enzymatic
activity? - Answers (D) Disulfide bonds between cysteine residues may become oxidized to dithiol
groups.
33. Below is a plot of Vo versus [S] for a specific allosteric enzyme under 3 different assay conditions...
Which of the following best describes the graph? - Answers (E) Plot #1 represents the effect of an
activator added to plot #2.
1. For the reaction A -----> B, ΔGo' = -32 kJ/mol.
The reaction is started in water (in a test-tube) with 10 mmol of A & 0 mmol B. After 48 hours,
chemical analysis revealed the presence of 8 mmol A, & 2 mmol B.
Which is the likely explanation? - Answers (B) Equilibrium has not been reached since B formation is
kinetically slow (
2. Which of the following statements is NOT correct: - Answers (A) If the Keq for a chemical reaction is
much smaller than its mass action ratio then the forward reaction is favored.
3. Acetyl-CoA hydrolase catalyzes the following reaction: acetyl-CoA + H20 → acetate + CoA. A
chemist is provided with the following information:
Oxaloacetate + acetyl-CoA + H20 → citrate + CoA ; ∆Go' = -32 kJ/mol
Oxaloacetate + acetate → citrate ; ∆Go' = -2 kJ/mol
From this information the biochemist concludes that the reaction catalyzed by acetyl-CoA hydrolase: -
Answers (C) is exothermic (or 'exergonic').
4. Complete the following sentence correctly. The majority of enzymes in a catabolic pathway... -
Answers (B) catalyze a reaction for which the equilibrium constant (Keq ) approximately equals the
mass action ratio
5. Under what special circumstance is the following equation the correct expression for the actual (in
vivo) free-energy change of the reaction A -----> B? G= = Go' + RTlnKeq - Answers (E) When the
reaction is at equilibrium in vivo.
6. The hydrolytic reaction: ATP + H20 ADP + Pi, has a standard free energy change, ∆Go' = -30.5 kJ/mol
The actual (in vivo) free energy change for this reaction in healthy red blood cells = ∆G' = -50 kJ/mol
What do these ∆Go' &/or ∆G' values tell us about ATP hydrolysis (to ADP + Pi)? - Answers (E) B & C are
both correct
(B) the equilibrium position for this reaction greatly favours the products, ADP + Pi
(C) this reaction is greatly displaced from equilibrium in the red blood cell
7. A new species of bacteria, Comparata biochemica, was discovered that catalyzes the following
reaction:
Lactate Ethanol + CO2
2026
Which of the following statements about the nature of enzyme catalysis is correct? - Answers d) An
enzyme greatly accelerates reaction rates by lowering the activation energy of a chemical reaction.
2. Which of the following statements about Michaelis-Menten enzyme kinetics is correct? - Answers
d) Km, the Michaelis constant, reflects the (apparent) affinity the enzyme has for its substrate.
3. Which of the following statements about competitive inhibition of an enzyme-catalyzed reaction is
correct? - Answers c) The enzyme's Vmax remains unchanged in the presence of a competitive
inhibitor. d
4. Which of the following statements about allosteric enzymes is correct? - Answers d) The 'native
form' of an allosteric enzyme can contain non-catalytic subunits.
5. Which of the following statements about competitive inhibition of an enzyme-catalyzed reaction is
correct? - Answers c) Competitive inhibition can be overcome by the addition of large amounts of
substrate to a reaction.
6. Which of the following statements about Michaelis-Menten kinetics are correct? - Answers e) B and
D are correct
b) A low Km values indicates a high affinity of an enzyme for its substrate. c
d) The Km of an enzyme is unchanged when the enzyme's concentration is increased. e
7. Which of the statements regarding enzymes is false? - Answers c) Enzymes shift the equilibrium
position of a chemical reaction in favor of the product(s).
8. When [S] = KM, the velocity of an enzyme catalyzed reaction is: - Answers d) 0.5 x Vmax.
9. β-galactosidase catalyzes the hydrolysis of the disaccharide lactose to yield glucose and galactose.
What other substrate does β-galactosidase require (apart from galactose)? - Answers c) H2O
10. Lactate dehydrogenase from human skeletal muscle and heart provides a good example of: -
Answers a) isozymes
11. The 'thermal kinetic window' corresponds to the temperature range over which an enzyme
displays: - Answers a) the minimal Km value for its substrate(s)
12. Any non-protein component that is absolutely required by an enzyme for it to have catalytic
activity is referred to as a: - Answers d) co-factor
13. In Mixed-Competitive inhibition of enzyme activity... - Answers b) The inhibitor can bind to the
free enzyme or the enzyme-substrate complex.
14. Which of the following statements about allosteric enzymes is false? - Answers c) Allosteric
effectors compete with the substrate for binding sites.
15. Q10 values for most enzymes from homeothermic (warm blooded) animal species are approx. 2.0,
whereas Q10 values for enzymes of many poikilothermic (cold blooded) species are often much less
than 2.0 (and sometimes close to 1.0). How might this help a poikilothermic animal adapt to its
environment? - Answers a) Metabolic processes are not as severely influenced by changes in
environmental temperature
16. Which of the following techniques or approaches has contributed to our understanding of the
structure of a metabolic pathway in a particular species? - Answers e) B and D are both correct
b) 'pulse-chase' radiolabeling studies
d) annotated genome sequence information
17. What domain of life do all known hyperthermophiles belong to? - Answers d) archaea
18. Which of the following statements completes the following sentence incorrectly?
The thermal stability of 'extremozymes' from hyperthermophiles arises from alterations in their
primary structure such that these proteins exhibit ... - Answers a) increased number of cysteine
residues (leading to more disulfide bridges)
19. An enzyme was determined to have a turnover number (kcat) of 10 sec-1. From the following
data, calculate the total amount of enzyme (in μmol) present during these experiments.
Substrate Concentration (mM): 0.1 0.2 0.4 0.6 10 100 Initial reaction velocity (μmol/minute): 67 128
334 476 600 600
Total Amount of Enzyme = - Answers c) 1 μmol
20. The enzyme phosphofructokinase (PFK) requires Mg2+ to catalyze the reaction: Fructose-6-
phosphate + ATP ----> Fructose-1,6-bisphosphate + ADP. In the absence of Mg2+, the enzyme would
be referred to as the PFK... - Answers (A) apoenzyme
, 21. The 'proteome': - Answers (B) is the set of expressed proteins in a specific cell type, at a given
time, under defined conditions.
22. About 100 years ago Lenoir Michaelis and that lovely Canadian icon Maud Menten derived their
MichaelisMenten equation to relate [S] to the initial rate (Vo) of an enzyme-catalyzed reaction. The
correct expression for their equation is: - Answers (A) Vo = (Vmax x [S]) ÷ (Km + [S])
24. Which of these statements about enzymes that display 'positive cooperativity' with respect to
substrate binding is false? - Answers (E) They can never be both 'homotropic' and 'hetrotropic'.
25. Pyridoxal phosphate is required by most transaminase enzymes as a(n) - Answers (D) co-enzyme
For Questions #26 to #30
β-galactosidase catalyzes the hydrolysis of the disaccharide lactose to yield glucose & galactose. The
enzyme purified from E. coli was used in kinetic studies at 37 oC and gave the following results. 26.
What is the minimal lactose concentration that saturates this enzyme? - Answers (A) 0.20 mM
27. In the presence of 2 mM glucose (a competitive inhibitor) the enzyme's affinity for lactose was
reduced by about 4-fold. What is the enzyme's approximate Km for lactose in the presence of 2 mM
glucose - Answers (B) 0.40 mM
28. Estimate the enzyme's turnover number (kcat value) from the above data. - Answers (E) 10 sec-1
29. Estimate the enzyme's catalytic efficiency from the above data. - Answers (C) 100 sec-1 mM-1
30. Which compound is often added to purification and activity assay buffers of oligomeric enzymes
(have quaternary structure) to help stabilize these enzymes in vitro? - Answers (A) glycerol
31. The maximum optimal growth temperature limit for life (= living & growing cells) is currently
believed to be about: - Answers (B) 125 oC
32. Which of the following is unlikely to be a possible reason for the pH dependence of enzymatic
activity? - Answers (D) Disulfide bonds between cysteine residues may become oxidized to dithiol
groups.
33. Below is a plot of Vo versus [S] for a specific allosteric enzyme under 3 different assay conditions...
Which of the following best describes the graph? - Answers (E) Plot #1 represents the effect of an
activator added to plot #2.
1. For the reaction A -----> B, ΔGo' = -32 kJ/mol.
The reaction is started in water (in a test-tube) with 10 mmol of A & 0 mmol B. After 48 hours,
chemical analysis revealed the presence of 8 mmol A, & 2 mmol B.
Which is the likely explanation? - Answers (B) Equilibrium has not been reached since B formation is
kinetically slow (
2. Which of the following statements is NOT correct: - Answers (A) If the Keq for a chemical reaction is
much smaller than its mass action ratio then the forward reaction is favored.
3. Acetyl-CoA hydrolase catalyzes the following reaction: acetyl-CoA + H20 → acetate + CoA. A
chemist is provided with the following information:
Oxaloacetate + acetyl-CoA + H20 → citrate + CoA ; ∆Go' = -32 kJ/mol
Oxaloacetate + acetate → citrate ; ∆Go' = -2 kJ/mol
From this information the biochemist concludes that the reaction catalyzed by acetyl-CoA hydrolase: -
Answers (C) is exothermic (or 'exergonic').
4. Complete the following sentence correctly. The majority of enzymes in a catabolic pathway... -
Answers (B) catalyze a reaction for which the equilibrium constant (Keq ) approximately equals the
mass action ratio
5. Under what special circumstance is the following equation the correct expression for the actual (in
vivo) free-energy change of the reaction A -----> B? G= = Go' + RTlnKeq - Answers (E) When the
reaction is at equilibrium in vivo.
6. The hydrolytic reaction: ATP + H20 ADP + Pi, has a standard free energy change, ∆Go' = -30.5 kJ/mol
The actual (in vivo) free energy change for this reaction in healthy red blood cells = ∆G' = -50 kJ/mol
What do these ∆Go' &/or ∆G' values tell us about ATP hydrolysis (to ADP + Pi)? - Answers (E) B & C are
both correct
(B) the equilibrium position for this reaction greatly favours the products, ADP + Pi
(C) this reaction is greatly displaced from equilibrium in the red blood cell
7. A new species of bacteria, Comparata biochemica, was discovered that catalyzes the following
reaction:
Lactate Ethanol + CO2
