In Photosytem-I (PSI) of light reaction which substrate works as an electron acceptor?

Options

A. `NAD^(+)`
B. `ADP`
C. `NADP^(+)`
D. `FADH^(+)`

Answer

To answer the question regarding which substrate works as an electron acceptor in Photosystem I (PSI) of the light reaction, we can break down the process step by step:

### Step-by-Step Solution:

1. **Understanding Photosystems**:
- Photosystem I (PSI) is one of the two photosystems involved in the light reactions of photosynthesis. It plays a crucial role in capturing light energy and converting it into chemical energy.

2. **Electron Transport Chain**:
- In the light reactions, electrons are excited by light energy and are transferred through a series of proteins in the thylakoid membrane. This process begins in Photosystem II (PSII) and continues to PSI.

3. **Role of PSI**:
- PSI receives electrons that have been energized by light. These electrons are passed to an electron acceptor.

4. **Identifying the Electron Acceptor**:
- The primary electron acceptor in PSI is a molecule known as NADP+ (Nicotinamide adenine dinucleotide phosphate).

5. **Formation of NADPH**:
- When PSI accepts the electrons, it reduces NADP+ to form NADPH. This reaction is crucial as NADPH is used in the Calvin cycle for the synthesis of glucose.

6. **Conclusion**:
- Therefore, the substrate that works as an electron acceptor in Photosystem I is NADP+.

### Final Answer:
The substrate that works as an electron acceptor in Photosystem I (PSI) of the light reaction is NADP+.

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