Which one directly transfers electrons to `NADP^(+)` during light reaction ?

Options

A. `PS` I
B. `PS` II
C. Cytochromes
D. Plastocyanin.

Answer

To answer the question "Which one directly transfers electrons to `NADP^(+)` during the light reaction?", we can break down the process of photosynthesis, particularly focusing on the light reactions that occur in the thylakoid membranes of chloroplasts.

### Step-by-Step Solution:

1. **Understanding Photosystems**:
- There are two main photosystems involved in the light reactions of photosynthesis: Photosystem II (PSII) and Photosystem I (PSI).
- PSII absorbs light energy and uses it to excite electrons, which are then transferred through a series of proteins.

2. **Electron Transport Chain**:
- The excited electrons from PSII are transferred to an electron transport chain, which includes a series of proteins and molecules, such as plastoquinone and cytochromes.
- As the electrons move through this chain, they help in the synthesis of ATP via chemiosmosis.

3. **Role of Photosystem I**:
- The electrons that reach PSI are again excited by light energy.
- The excited electrons from PSI are transferred to NADP^(+) to form NADPH.

4. **Direct Transfer to NADP^(+)**:
- The key point is that the electrons from PSI are the ones that directly reduce NADP^(+) to NADPH.
- This means that PSI is responsible for the direct transfer of electrons to NADP^(+).

5. **Conclusion**:
- Therefore, the correct answer to the question is that Photosystem I (PSI) directly transfers electrons to NADP^(+) during the light reaction.

### Final Answer:
**Photosystem I (PSI)** directly transfers electrons to `NADP^(+)` during the light reaction.

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