Bioenergetics MCQs for GPAT, NIPER, AIIMS Pharmacist, Railway Pharmacist, SSC, ESIC, and State Pharmacist Examinations

These questions focus on conceptual understanding, numerical reasoning, and tricky applications commonly seen in competitive pharmacy examinations.

1. For a biochemical reaction occurring at constant temperature and pressure:

ΔG=ΔH−TΔS

A reaction will proceed spontaneously when:

A. ΔG > 0
B. ΔG = 0
C. ΔG < 0
D. ΔH > 0 and ΔS < 0

Answer: C. ΔG < 0

Explanation:

Negative Gibbs free energy indicates a spontaneous (exergonic) process. Positive ΔG indicates a non-spontaneous reaction requiring energy input.

2. Which combination always guarantees a spontaneous reaction at all temperatures?

A. ΔH > 0 and ΔS > 0
B. ΔH < 0 and ΔS < 0
C. ΔH < 0 and ΔS > 0
D. ΔH > 0 and ΔS < 0

Answer: C. ΔH < 0 and ΔS > 0

Explanation:

A negative enthalpy change and positive entropy change both favor spontaneity, making ΔG negative irrespective of temperature.

3. A reaction has:

• ΔH = +40 kJ/mol

• ΔS = +200 J/mol·K

At what temperature will the reaction become spontaneous?

A. Above 100 K
B. Above 200 K
C. Above 300 K
D. Above 400 K

Answer: B. Above 200 K

Explanation:

Convert entropy:

ΔS=0.2 kJ/mol⋅K

At equilibrium:

ΔG=0

T= ΔH​/ΔS = 40/0.2​ = 200K

The reaction becomes spontaneous above 200 K.

4. At equilibrium, the value of Gibbs free energy change is:

A. Positive
B. Negative
C. Zero
D. Equal to enthalpy

Answer: C. Zero

Explanation:

At equilibrium there is no driving force for reaction progress.

ΔG=0

MCQ 5

Which statement regarding ATP hydrolysis is correct?

A. ATP contains unstable covalent bonds that explode on hydrolysis.
B. ATP hydrolysis releases energy because products are more stable than reactants.
C. ATP hydrolysis is endergonic.
D. ATP stores energy in phosphate atoms.

Answer: B. ATP hydrolysis releases energy because products are more stable than reactants.

Explanation:

Energy is released because ADP and inorganic phosphate are more stable due to resonance stabilization and reduced electrostatic repulsion.

MCQ 6

The standard free energy change for ATP hydrolysis under physiological conditions is approximately:

A. −7.3 kcal/mol
B. +7.3 kcal/mol
C. −73 kcal/mol
D. +73 kcal/mol

Answer: A. −7.3 kcal/mol

Explanation:

The standard free energy of ATP hydrolysis is approximately:

[
\Delta G^\circ' = -7.3 \text{ kcal/mol}
]

or approximately −30.5 kJ/mol.

MCQ 7

Which of the following has the highest phosphoryl group transfer potential?

A. Glucose-6-phosphate
B. ATP
C. Phosphoenolpyruvate
D. Glycerol-3-phosphate

Answer: C. Phosphoenolpyruvate

Explanation:

PEP has an extremely high free energy of hydrolysis (~−61.9 kJ/mol), greater than ATP.

Order:

PEP > Creatine phosphate > ATP > Glucose-6-phosphate

MCQ 8

Which compound can directly phosphorylate ADP to ATP during glycolysis?

A. Glucose-6-phosphate
B. Phosphoenolpyruvate
C. Fructose-6-phosphate
D. Ribose-5-phosphate

Answer: B. Phosphoenolpyruvate

Explanation:

PEP transfers phosphate to ADP via pyruvate kinase reaction.

MCQ 9

Which nucleotide triphosphate is primarily used in protein synthesis?

A. ATP
B. GTP
C. CTP
D. UTP

Answer: B. GTP

Explanation:

GTP provides energy during initiation, elongation, and translocation steps of translation.

MCQ 10

UTP is mainly involved in:

A. Protein synthesis
B. Glycogen synthesis
C. Oxidative phosphorylation
D. DNA replication

Answer: B. Glycogen synthesis

Explanation:

UTP forms UDP-glucose, the activated intermediate required for glycogen synthesis.

MCQ 11

Which nucleotide triphosphate is primarily required for phospholipid synthesis?

A. ATP
B. GTP
C. CTP
D. TTP

Answer: C. CTP

Explanation:

CTP forms activated intermediates such as CDP-choline and CDP-diacylglycerol in phospholipid synthesis.

MCQ 12

The oxidizing agent in a redox reaction is the substance that:

A. Loses electrons
B. Gains electrons
C. Donates hydrogen
D. Undergoes oxidation

Answer: B. Gains electrons

Explanation:

Oxidizing agents accept electrons and themselves become reduced.

MCQ 13

A redox couple with a more positive reduction potential tends to:

A. Donate electrons readily
B. Accept electrons readily
C. Remain chemically inert
D. Undergo oxidation

Answer: B. Accept electrons readily

Explanation:

The more positive the reduction potential, the greater the tendency to accept electrons.

MCQ 14

Electron flow in the electron transport chain occurs from:

A. Higher reduction potential to lower reduction potential
B. Lower reduction potential to higher reduction potential
C. ATP to NADH
D. Oxygen to NADH

Answer: B. Lower reduction potential to higher reduction potential

Explanation:

Electrons move spontaneously toward increasingly positive reduction potentials, ultimately reaching oxygen.

MCQ 15

Which component has the highest reduction potential in the electron transport chain?

A. NADH
B. FMN
C. Cytochrome c
D. Oxygen

Answer: D. Oxygen

Explanation:

Oxygen has the highest reduction potential and acts as the final electron acceptor.

MCQ 16

If ΔG for a reaction is positive, the reaction can still proceed if:

A. Temperature decreases
B. Coupled to ATP hydrolysis
C. Entropy decreases
D. Enthalpy increases

Answer: B. Coupled to ATP hydrolysis

Explanation:

Cells drive unfavorable reactions by coupling them to highly favorable ATP hydrolysis.

MCQ 17

Which of the following is an example of an endergonic process?

A. ATP hydrolysis
B. Oxidation of glucose
C. Glycogen synthesis
D. Electron transport

Answer: C. Glycogen synthesis

Explanation:

Glycogen synthesis requires energy input and is therefore endergonic.

MCQ 18

The major reason ATP is considered the "energy currency" of the cell is that:

A. It contains the highest-energy phosphate bond known in biology.
B. It can couple exergonic and endergonic reactions efficiently.
C. It is present only in mitochondria.
D. ATP is more stable than ADP.

Answer: B. It can couple exergonic and endergonic reactions efficiently.

Explanation:

ATP acts as an intermediate energy carrier linking catabolism with anabolism.

MCQ 19

Which statement regarding entropy is correct?

A. Entropy is the measure of energy content.
B. Entropy measures the degree of disorder or randomness.
C. Entropy is always negative in biological systems.
D. Entropy is independent of temperature.

Answer: B. Entropy measures the degree of disorder or randomness.

Explanation:

Higher entropy corresponds to greater molecular disorder and energy dispersal.

MCQ 20

During ATP hydrolysis:

ATP + H₂O → ADP + Pi

The reaction is:

A. Oxidation reaction only
B. Reduction reaction only
C. Hydrolysis reaction with negative free energy change
D. Condensation reaction

Answer: C. Hydrolysis reaction with negative free energy change

Explanation:

ATP hydrolysis is an exergonic hydrolysis reaction with a negative ΔG.

MCQ 21 (GPAT/NIPER Level)

Which statement is TRUE regarding free energy and equilibrium constant?

A. ΔG°' and K_eq are unrelated.
B. A large K_eq corresponds to positive ΔG°'.
C. A large K_eq corresponds to negative ΔG°'.
D. K_eq is independent of free energy.

Answer: C. A large K_eq corresponds to negative ΔG°'.

Explanation:

[
\Delta G^\circ' = -RT \ln K_{eq}
]

If K_eq > 1, lnK_eq is positive and ΔG°' becomes negative.

MCQ 22 (Previous-Year Pattern)

Which pair is correctly matched?

A. ATP — Glycogen synthesis
B. GTP — Translation
C. CTP — Muscle contraction
D. UTP — Electron transport chain

Answer: B. GTP — Translation

Explanation:

• ATP → General energy currency

• GTP → Protein synthesis

• UTP → Glycogen synthesis

• CTP → Phospholipid synthesis

MCQ 23 (Highly Conceptual)

A reaction has:

• ΔH = −50 kJ/mol

• ΔS = −100 J/mol·K

This reaction is:

A. Spontaneous at all temperatures
B. Never spontaneous
C. Spontaneous only at low temperatures
D. Spontaneous only at high temperatures

Answer: C. Spontaneous only at low temperatures

Explanation:

Since both ΔH and TΔS are negative:

[
\Delta G=\Delta H-T\Delta S
]

At high temperature, the positive value of (-T\Delta S) becomes large and may make ΔG positive.

MCQ 24 (NIPER Conceptual Trap)

Which statement is FALSE?

A. ATP hydrolysis is exergonic.
B. Oxygen has a high reduction potential.
C. ATP has the highest phosphoryl transfer potential in the cell.
D. GTP participates in protein synthesis.

Answer: C. ATP has the highest phosphoryl transfer potential in the cell.

Explanation:

Several compounds possess higher phosphoryl transfer potential than ATP, including:

• Phosphoenolpyruvate

• Creatine phosphate

• 1,3-Bisphosphoglycerate

MCQ 25

Which of the following is classified as a high-energy phosphate compound?

A. Glucose
B. AMP
C. Creatine phosphate
D. Ribose

Answer: C. Creatine phosphate

Explanation:

Creatine phosphate serves as a rapid reserve of high-energy phosphate in skeletal muscle and can regenerate ATP via creatine kinase reaction.