During light reaction of Photosynthesis the electrons lost by pigment system II are compensated by

Options

A. `CO_2`
B. `H_2O`
C. `O_2`
D. ATP

Answer

**Step-by-Step Solution:**

1. **Understanding Light Reactions**: The light reactions of photosynthesis occur in the thylakoid membranes of chloroplasts and are also referred to as light-dependent reactions. They require light energy to produce ATP and NADPH.

2. **Role of Pigment Systems**: In the light reactions, there are two main pigment systems: Photosystem I (PSI) and Photosystem II (PSII). Each of these systems plays a crucial role in capturing light energy and facilitating the transfer of electrons.

3. **Electron Loss in PSII**: During the light reaction, Photosystem II absorbs light energy, which excites electrons. These electrons are then transferred through a series of proteins in the electron transport chain. However, this process results in the loss of electrons from PSII.

4. **Compensation for Lost Electrons**: The electrons lost by Photosystem II are compensated by the process of photolysis, which is the splitting of water molecules (H2O) in the presence of light. This process provides the necessary electrons to replace those lost by PSII.

5. **Products of Photolysis**: The photolysis of water results in the production of hydrogen ions (H+), electrons (which replace those lost by PSII), and oxygen (O2), which is released as a byproduct.

6. **Conclusion**: Therefore, during the light reactions of photosynthesis, the electrons lost by pigment system II (Photosystem II) are compensated by the electrons derived from the photolysis of water (H2O).

**Final Answer**: The electrons lost by pigment system II are compensated by water (H2O).

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