The first electron acceptor in photosystem-I of cyclic photophosphorylation is

Options

A. Cytochrome
B. Plastocyanin
C. Ferrodoxin
D. Plastoquinone

Answer

**Step-by-Step Solution:**

1. **Understanding Cyclic Photophosphorylation**: Cyclic photophosphorylation is a process that occurs in photosystem I (PSI) where light energy is used to produce ATP. It involves the movement of electrons through a series of proteins.

2. **Identifying Photosystem I**: The reaction center of photosystem I is chlorophyll a, which absorbs light at a wavelength of 700 nanometers, denoted as P700.

3. **Excitation of Electrons**: When chlorophyll a absorbs light energy, it becomes excited and releases high-energy electrons.

4. **First Electron Acceptor**: The first molecule to accept the excited electrons from photosystem I is ferredoxin. This is crucial in the cyclic photophosphorylation pathway.

5. **Electron Transport Chain**: After ferredoxin accepts the electrons, they are transferred to cytochrome b6, then to cytochrome f, and finally to plastocyanin. This series of transfers is essential for the production of ATP.

6. **Returning Electrons**: In cyclic photophosphorylation, the electrons eventually return to photosystem I, completing the cycle.

7. **Conclusion**: Therefore, the first electron acceptor in photosystem I of cyclic photophosphorylation is ferredoxin.

**Final Answer**: Ferredoxin

---