Page 1 of 149
Biochemistry Module 3 Exam Newest
Questions and Answers (Verified Answers).
1. The standard free energy change (ΔG°') for ATP hydrolysis
is approximately:
a) +7.3 kcal/mol
b) –7.3 kcal/mol
c) –3.0 kcal/mol
d) 0 kcal/mol
Answer: b) –7.3 kcal/mol
Rationale: ATP → ADP + Pi releases 7.3 kcal/mol under
,Page 2 of 149
standard conditions; actual cellular ΔG is more negative (~ –
12 to –14).
Q2. Which of the following reactions is most likely to be
coupled to ATP hydrolysis in the cell?
a) Glucose + fructose → sucrose (ΔG°' = +5.5 kcal/mol)
b) Creatine phosphate → creatine + Pi (ΔG°' = –10.3
kcal/mol)
c) CO2 + H2O → H2CO3 (ΔG°' = +2.0 kcal/mol)
d) Pyruvate → lactate (ΔG°' = –3.0 kcal/mol)
Answer: a) Glucose + fructose → sucrose
Rationale: Endergonic reactions (positive ΔG) require coupling
to exergonic ones like ATP hydrolysis.
Q3. A reaction has ΔG°' = –5.0 kcal/mol. At equilibrium, the
Keq will be:
a) <1
b) =1
c) >1
,Page 3 of 149
d) Cannot be determined
Answer: c) >1
Rationale: ΔG°' = –RT ln Keq. Negative ΔG°' means ln Keq
positive → Keq > 1.
Q4. Scenario: A researcher measures ΔG for a reaction in a
cell and finds it to be –8.0 kcal/mol, but the ΔG°' for the same
reaction is +2.0 kcal/mol. What explains this?
a) The reaction is at equilibrium
b) The cellular concentrations of products are very low
c) The cellular concentrations of reactants are very low
d) Temperature is higher than 25°C
Answer: b) The cellular concentrations of products are very
low
Rationale: ΔG = ΔG°' + RT ln([products]/[reactants]). Low
product concentration makes the ratio small, driving ΔG
negative despite positive ΔG°'.
, Page 4 of 149
Q5. Which of the following has the highest phosphoryl transfer
potential?
a) ATP
b) Glucose-6-phosphate
c) Phosphoenolpyruvate (PEP)
d) AMP
Answer: c) Phosphoenolpyruvate (PEP)
Rationale: PEP hydrolysis ΔG°' ≈ –14.8 kcal/mol, higher than
ATP's –7.3.
Q6. The term "high-energy bond" in ATP refers to:
a) The hydrogen bonds between adenine and ribose
b) The phosphoanhydride bonds between phosphates
c) The glycosidic bond between ribose and adenine
d) The ester bond between ribose and first phosphate
Answer: b) The phosphoanhydride bonds between phosphates
Rationale: These bonds have large negative ΔG of hydrolysis
Biochemistry Module 3 Exam Newest
Questions and Answers (Verified Answers).
1. The standard free energy change (ΔG°') for ATP hydrolysis
is approximately:
a) +7.3 kcal/mol
b) –7.3 kcal/mol
c) –3.0 kcal/mol
d) 0 kcal/mol
Answer: b) –7.3 kcal/mol
Rationale: ATP → ADP + Pi releases 7.3 kcal/mol under
,Page 2 of 149
standard conditions; actual cellular ΔG is more negative (~ –
12 to –14).
Q2. Which of the following reactions is most likely to be
coupled to ATP hydrolysis in the cell?
a) Glucose + fructose → sucrose (ΔG°' = +5.5 kcal/mol)
b) Creatine phosphate → creatine + Pi (ΔG°' = –10.3
kcal/mol)
c) CO2 + H2O → H2CO3 (ΔG°' = +2.0 kcal/mol)
d) Pyruvate → lactate (ΔG°' = –3.0 kcal/mol)
Answer: a) Glucose + fructose → sucrose
Rationale: Endergonic reactions (positive ΔG) require coupling
to exergonic ones like ATP hydrolysis.
Q3. A reaction has ΔG°' = –5.0 kcal/mol. At equilibrium, the
Keq will be:
a) <1
b) =1
c) >1
,Page 3 of 149
d) Cannot be determined
Answer: c) >1
Rationale: ΔG°' = –RT ln Keq. Negative ΔG°' means ln Keq
positive → Keq > 1.
Q4. Scenario: A researcher measures ΔG for a reaction in a
cell and finds it to be –8.0 kcal/mol, but the ΔG°' for the same
reaction is +2.0 kcal/mol. What explains this?
a) The reaction is at equilibrium
b) The cellular concentrations of products are very low
c) The cellular concentrations of reactants are very low
d) Temperature is higher than 25°C
Answer: b) The cellular concentrations of products are very
low
Rationale: ΔG = ΔG°' + RT ln([products]/[reactants]). Low
product concentration makes the ratio small, driving ΔG
negative despite positive ΔG°'.
, Page 4 of 149
Q5. Which of the following has the highest phosphoryl transfer
potential?
a) ATP
b) Glucose-6-phosphate
c) Phosphoenolpyruvate (PEP)
d) AMP
Answer: c) Phosphoenolpyruvate (PEP)
Rationale: PEP hydrolysis ΔG°' ≈ –14.8 kcal/mol, higher than
ATP's –7.3.
Q6. The term "high-energy bond" in ATP refers to:
a) The hydrogen bonds between adenine and ribose
b) The phosphoanhydride bonds between phosphates
c) The glycosidic bond between ribose and adenine
d) The ester bond between ribose and first phosphate
Answer: b) The phosphoanhydride bonds between phosphates
Rationale: These bonds have large negative ΔG of hydrolysis
