During cyclic photophosphoryltion, which of following events does not occur

Options

A. Electrons are transferred back to `P_(680)`
B. `NADP^(+)` is not available as an electron acceptor
C. NADPH will not be oxidised
D. electrons from photosystem I are not passed to NADP+

Answer

### Step-by-Step Solution:

1. **Understanding Photophosphorylation**:
- Photophosphorylation refers to the process of synthesizing ATP using light energy. It occurs in two forms: cyclic and non-cyclic photophosphorylation.

2. **Identifying the Types**:
- Non-cyclic photophosphorylation involves both Photosystem I (PSI) and Photosystem II (PSII), leading to the production of ATP and NADPH.
- Cyclic photophosphorylation, on the other hand, involves only Photosystem I.

3. **Function of Photosystem I**:
- In cyclic photophosphorylation, the reaction center of Photosystem I is known as P700. This system absorbs light and facilitates the flow of electrons.

4. **Key Events in Cyclic Photophosphorylation**:
- Only ATP is synthesized during cyclic photophosphorylation.
- Electrons are cycled back to Photosystem I, which means they do not reduce NADP+ to form NADPH.
- The absence of Photosystem II and NADP reductase enzyme is crucial, as these components are necessary for NADPH synthesis.

5. **Identifying the Incorrect Event**:
- Since cyclic photophosphorylation does not produce NADPH, any statement suggesting that NADPH is produced or that PSII is involved would be incorrect.

6. **Conclusion**:
- The event that does not occur during cyclic photophosphorylation is the synthesis of NADPH.