In cyclic photophosphorylation, ATP is synthesized when electron passes from

Options

A. ferredoxin to cytochrome `b_(6)`
B. plastoquinone to cytochrome ƒ
C. ferredoxin to plastoquinone and cytochrome `b_(6)` to cytochrome ƒ
D. all the above are wrong

Answer

To answer the question regarding the synthesis of ATP in cyclic photophosphorylation, we can break down the process step by step.

### Step-by-Step Solution:

1. **Understanding Cyclic Photophosphorylation**:
- Cyclic photophosphorylation is a process that occurs in the thylakoid membranes of chloroplasts, where light energy is used to convert ADP to ATP.

2. **Role of Photosystems**:
- The process begins with the absorption of light by Photosystem I (PSI). This light energy excites electrons, initiating their movement.

3. **Electron Transport Chain**:
- The excited electrons from PSI are transferred to a series of electron carriers. In cyclic photophosphorylation, the electrons move in a circular path.
- The pathway includes:
- **Ferredoxin**: The first electron carrier that receives electrons from PSI.
- **Plastoquinone**: The next carrier that receives electrons from ferredoxin.
- **Cytochrome b6**: The electron then moves to cytochrome b6.
- **Cytochrome f**: Finally, the electrons are transferred to cytochrome f.

4. **ATP Synthesis**:
- As the electrons move through these carriers, they release energy, which is used to pump protons (H+) into the thylakoid lumen, creating a proton gradient.
- This gradient drives ATP synthase, an enzyme that synthesizes ATP from ADP and inorganic phosphate (Pi).

5. **Conclusion**:
- In summary, in cyclic photophosphorylation, ATP is synthesized when electrons pass from ferredoxin to plastoquinone and then to cytochrome b6 and cytochrome f.

### Final Answer:
In cyclic photophosphorylation, ATP is synthesized when electrons pass from **ferredoxin to plastoquinone and from cytochrome b6 to cytochrome f**.