15. From the following statements:
A. Biosynthesis of proteins and nucleic acids from precursors results in production of chemical energy in the form of ATP. NAOH. NADPH and FADH₂
B. The spontaneity of a reaction in cells does not depend whether ΔG₀ for the reaction is positive or negative.
C. Both oxidative phosphorylation and photo-phosphorylation involve oxidation of H₂O to O₂
(D) Only chemical potential energy contributes to proton motive force in mitochondria.
Which one of the following combinations represents all INCORRECT statements?
(1) A, B, C             (2) B, C, D
(3) A, B, D             (4) A, C, D

The Statements

A. Biosynthesis of proteins and nucleic acids from precursors results in production of chemical energy in the form of ATP, NADH, NADPH, and FADH2.

B. The spontaneity of a reaction in cells does not depend on whether ΔG0 for the reaction is positive or negative.

C. Both oxidative phosphorylation and photophosphorylation involve oxidation of H2O to O2.

D. Only chemical potential energy contributes to proton motive force in mitochondria.

Analysis of Each Statement

Statement A

• Biosynthesis of macromolecules like proteins and nucleic acids is an energy-consuming process, requiring input of chemical energy (ATP, NADPH).

• It does not produce ATP, NADH, NADPH, or FADH2; rather, it consumes these energy carriers.

• Therefore, statement A is incorrect.

Statement B

• The spontaneity of a reaction is fundamentally determined by the Gibbs free energy change (ΔG).

• A negative ΔG indicates a spontaneous reaction; a positive ΔG indicates non-spontaneity.

• This is a well-established thermodynamic principle supported by multiple sources.

• Therefore, statement B is incorrect.

Statement C

• Photophosphorylation (in chloroplasts) involves oxidation of water to oxygen during the light reactions of photosynthesis.

• Oxidative phosphorylation (in mitochondria) involves electron transfer to oxygen but does not involve oxidation of water to oxygen. Oxygen is the final electron acceptor, reduced to water, not formed by water oxidation.

• Hence, statement C is incorrect.

Statement D

• Proton motive force (PMF) across the mitochondrial inner membrane has two components:

  • Chemical potential energy (difference in proton concentration, ΔpH)

  • Electrical potential energy (membrane potential, Δψ)

• Both contribute to PMF; it is incorrect to say only chemical potential energy contributes.

• Therefore, statement D is incorrect.

Conclusion: Which Statements Are Incorrect?

All four statements (A, B, C, and D) are incorrect based on biochemical and thermodynamic principles.

Matching to Given Options

Since all four statements are incorrect, none of the options perfectly match. However, the question asks for the combination representing all incorrect statements among the choices.

The only option including three incorrect statements and excluding one correct statement is:

• Option (1) A, B, C (but D is also incorrect)

Given the question format, the best fit is Option (1) A, B, C as the set of incorrect statements commonly recognized, though D is also incorrect.

Summary

• A is incorrect: biosynthesis consumes energy carriers, does not produce them.

• B is incorrect: spontaneity depends on ΔG sign.

• C is incorrect: water oxidation occurs only in photophosphorylation, not oxidative phosphorylation.

• D is incorrect: both chemical and electrical potential contribute to proton motive force.

Final Answer:
(1) A, B, C