Chemiosmotic theory of ATP synthesis in chloroplast & mitochondria is proposed by

Options

A. Mitchell
B. Arnon
C. Emerson
D. Hill

Answer

**Step-by-Step Text Solution:**

1. **Understanding the Chemiosmotic Theory**: The chemiosmotic theory explains how ATP is synthesized in both chloroplasts and mitochondria. It is based on the concept of a proton gradient across a membrane.

2. **Identifying the Scientists**: The question provides four names: Michel, Arnan, Emerson, and Hel. We need to determine which of these scientists proposed the chemiosmotic theory.

3. **Reviewing Contributions**:
- **Emerson**: Proposed the two pigment system theory, which is not related to the chemiosmotic theory.
- **Hel**: Suggested that the evolution of oxygen occurs during the light reactions of photosynthesis, but did not propose the chemiosmotic theory.
- **Arnan**: Described how green plants utilize light energy to produce chemical energy and oxygen, but again, this is not related to the chemiosmotic theory.
- **Michel**: Proposed the chemiosmotic theory in 1961, which explains ATP production through a proton gradient.

4. **Conclusion**: Based on the contributions of each scientist, the correct answer to the question is **Peter Michel**.

5. **Explanation of the Chemiosmotic Theory**: According to this theory, ATP production results from a proton (H+) gradient across the thylakoid membrane in chloroplasts and the inner mitochondrial membrane. The flow of protons back across the membrane through ATP synthase drives the synthesis of ATP from ADP and inorganic phosphate.

6. **Components Involved**: The essential components for chemiosmosis include:
- Proton gradient (H+ gradient)
- Proton pumps
- ATP synthase (composed of F0 and F1 subunits)

7. **Final Answer**: The chemiosmotic theory of ATP synthesis in chloroplasts and mitochondria was proposed by **Peter Michel** in 1961.

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