The correct option is NADP+.
Explanation
Photosynthesis consists of two main stages: the light-dependent reactions (light reactions) and the light-independent reactions (Calvin cycle). The light reactions occur in the thylakoid membranes of chloroplasts and involve the generation of ATP and NADPH through electron transport chains.
Detailed Analysis:
- NADP+ (Nicotinamide Adenine Dinucleotide Phosphate): In the non-cyclic electron transport chain (Z-scheme), electrons are initially released from the photolysis of water and travel through Photosystem II and Photosystem I. The final step involves the transfer of these electrons to NADP+ by the enzyme NADP reductase. Consequently, NADP+ is reduced to NADPH, making it the final electron acceptor in the light reaction.
- O2 (Oxygen): Oxygen is produced as a byproduct of the photolysis of water in Photosystem II. It is not an electron acceptor in photosynthesis; rather, it is the final electron acceptor in the electron transport chain of aerobic respiration.
- ADP (Adenosine Diphosphate): ADP is converted to ATP during the light reaction through a process called photophosphorylation. While it accepts a phosphate group, it does not serve as the terminal acceptor for the electron transport chain itself.
- FAD (Flavin Adenine Dinucleotide): FAD acts as an electron carrier primarily in the Krebs cycle of cellular respiration, not in the light reactions of photosynthesis.
Key Takeaway:
In the light-dependent reactions of photosynthesis, NADP+ serves as the final electron acceptor, resulting in the formation of NADPH, which is subsequently used in the dark reactions for carbon fixation.