`ATP` formation in chloroplast and mitochondrion is explained by

Options

A. Chemiosmotic theory
B. Munch's hypothesis (mass flow model)
C. Relay pump theory of Godlewski
D. Cholodny-Went's model

Answer

To answer the question regarding the explanation of ATP formation in chloroplasts and mitochondria, we can break down the solution into the following steps:

### Step-by-Step Solution

1. **Identify the Question**: The question asks about the theory that explains ATP formation in chloroplasts and mitochondria.

2. **List the Options**: The options provided are:
- 1. Chemiosmotic theory
- 2. Munch's hypothesis (mass flow model)
- 3. Relay pump theory of Godlewski
- 4. Colondi-Wendt's model

3. **Select the Correct Answer**: The correct answer is the **Chemiosmotic theory**. This theory was proposed by Peter Michaelis.

4. **Explain the Chemiosmotic Theory in Chloroplasts**:
- During photosynthesis in chloroplasts, there is an increase in the concentration of hydrogen ions (H⁺) inside the lumen of the thylakoids.
- These H⁺ ions move along their concentration gradient through a structure called the **coupling factor** (or ATP synthase).
- The movement of H⁺ ions through ATP synthase leads to the phosphorylation of ADP, resulting in the formation of ATP.

5. **Explain the Chemiosmotic Theory in Mitochondria**:
- Mitochondria are double membrane-bound organelles with an outer membrane and an inner membrane that is folded into structures called **cristae**.
- During the electron transport chain in cellular respiration, H⁺ ions accumulate in the intermembrane space.
- These H⁺ ions then flow back into the mitochondrial matrix through a structure known as **oxizome** (similar to the coupling factor in chloroplasts).
- The flow of H⁺ ions through ATP synthase in the matrix also leads to the formation of ATP from ADP and inorganic phosphate.

6. **Conclusion**: The chemiosmotic theory explains ATP formation in both chloroplasts and mitochondria through the movement of H⁺ ions along their concentration gradients, resulting in ATP synthesis.

### Final Answer
The correct explanation for ATP formation in chloroplasts and mitochondria is provided by the **Chemiosmotic theory**.

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