Chemiosmotic hypothesis for generation of ATP during light reaction was fist explained by

Options

A. Hill
B. Arnold
C. P. Mithchell
D. Van Niel

Answer

### Step-by-Step Solution:

1. **Understanding the Chemiosmotic Hypothesis**: The chemiosmotic hypothesis explains how ATP is generated during the light reactions of photosynthesis and respiration. It involves the movement of protons (H⁺ ions) across a membrane, creating a proton gradient.

2. **Identifying the Contributor**: The chemiosmotic hypothesis was first explained by Peter Mitchell in 1961. He proposed that the energy from electron transport chains is used to pump protons across a membrane, leading to a concentration gradient.

3. **Mechanism of ATP Generation**:
- **Proton Gradient Formation**: During the light reactions, protons are pumped into the thylakoid lumen of chloroplasts, creating a high concentration of protons inside the lumen compared to the stroma.
- **ATP Synthase Function**: The protons then flow back into the stroma through ATP synthase, a protein complex that synthesizes ATP from ADP and inorganic phosphate (Pi) as protons move through it.

4. **Role of Osmosis**: The movement of protons from an area of higher concentration (inside the lumen) to an area of lower concentration (the stroma) is akin to osmosis, which is the movement of solvent molecules across a selectively permeable membrane.

5. **Conclusion**: The chemiosmotic hypothesis is crucial for understanding how ATP is produced during the light reactions of photosynthesis and was first articulated by Peter Mitchell.

### Final Answer:
The chemiosmotic hypothesis for the generation of ATP during the light reaction was first explained by **Peter Mitchell** in 1961.

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