In the light reactions of photosynthesis, which molecule acts as the final electron acceptor in the electron transport chain?

• A. NADP\(^+\)
• B. O\(_2\)
• C. ATP
• D. Glucose

Answer: (A)

Verified step by step guidance

1. Understand the light reactions of photosynthesis: These occur in the thylakoid membranes of chloroplasts and involve the absorption of light energy to drive the transfer of electrons through the electron transport chain.
2. Identify the role of the electron transport chain: The chain transfers electrons from water molecules (H\(_2\)O) to a final electron acceptor, generating energy in the form of ATP and NADPH.
3. Recall the final electron acceptor in the light reactions: The molecule NADP\(^+\) (nicotinamide adenine dinucleotide phosphate) acts as the final electron acceptor, combining with electrons and protons to form NADPH.
4. Eliminate incorrect options: O\(_2\) is not involved as the final electron acceptor in the light reactions; it is a byproduct of water splitting. ATP is an energy carrier, not an electron acceptor. Glucose is produced later in the Calvin cycle, not during the light reactions.
5. Conclude that NADP\(^+\) is the correct answer: It plays a critical role in photosynthesis by accepting electrons and protons to form NADPH, which is used in the Calvin cycle for carbon fixation.