How does PS-I get supply of electrons continuously ?

Options

A. by removing from photon
B. by removing from ferredoxin
C. by removing from `CO_(2)`
D. by removing from plastocyanin

Answer

**Step-by-Step Solution:**

1. **Understanding Photosystems**: Photosystem I (PS-I) is also known as P700 because it absorbs light at wavelengths greater than 700 nm. In contrast, Photosystem II (PS-II) is known as P680, as it absorbs light at wavelengths less than 680 nm.

2. **Light Absorption by PS-II**: The process begins with PS-II absorbing light energy. This light energy excites the electrons in PS-II, promoting them to a higher energy state.

3. **Electron Transport Chain**: The excited electrons from PS-II are transferred to an electron carrier called Plastoquinone. Plastoquinone carries these electrons to the cytochrome complex.

4. **Energy Transfer to Plastocyanin**: The cytochrome complex then transfers the energy from the electrons to another carrier protein known as Plastocyanin, which contains copper.

5. **Electron Supply to PS-I**: Plastocyanin channels the energy and electrons to PS-I. When PS-I receives these electrons, it absorbs the energy, further exciting the electrons in PS-I to a higher energy state.

6. **Role of Ferredoxin**: The excited electrons in PS-I are then transferred to Ferredoxin, which acts as another electron carrier.

7. **Formation of NADH**: Ferredoxin then transfers the energy to NAD+ (Nicotinamide adenine dinucleotide), converting it into NADH. This NADH is crucial for the Calvin cycle, which synthesizes sugars.

8. **Continuous Supply of Electrons**: Thus, PS-I continuously receives electrons from Plastocyanin, ensuring a steady supply for the photosynthetic process.

**Final Answer**: PS-I gets a continuous supply of electrons by receiving them from Plastocyanin.

---