In non-cyclic photophosphorylation, PS `I` is reduced by

Options

A. Electron from PS `II`
B. Electron from ferredoxin
C. Hydrogen from water
D. Hydrogen from PS `II`.

Answer

To answer the question "In non-cyclic photophosphorylation, PS I is reduced by," we need to understand the process of non-cyclic photophosphorylation and the role of the photosystems involved.

### Step-by-Step Solution:

1. **Understanding Non-Cyclic Photophosphorylation**:
- Non-cyclic photophosphorylation is a process that occurs during the light-dependent reactions of photosynthesis. It involves the flow of electrons through two photosystems: Photosystem II (PS II) and Photosystem I (PS I).

2. **Role of Photosystem II**:
- In this process, light energy is absorbed by PS II, which excites electrons. These high-energy electrons are then transferred to an electron transport chain.

3. **Electron Transport Chain**:
- The electrons move through the electron transport chain, which includes various proteins and carriers. One important carrier in this chain is plastocyanin, which transports electrons between PS II and PS I.

4. **Reduction of Photosystem I**:
- As the electrons move through the chain, they eventually reach PS I. Here, the electrons from PS II are used to reduce PS I. This means that PS I gains electrons, which is referred to as reduction.

5. **Conclusion**:
- Therefore, in non-cyclic photophosphorylation, PS I is reduced by electrons that come from Photosystem II.

### Final Answer:
In non-cyclic photophosphorylation, PS I is reduced by electrons from Photosystem II.

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