According to the chemi-osmotic mechaniosm for ATP synthesis given by P. Mitchell, the force/factor responsible for ATP synthesis is

Options

A. Membrane potential across membrane
B. Proton motive force
C. Electron motive force
D. Redox potential

Answer

**Step-by-Step Solution:**

1. **Understanding the Chemiosmotic Mechanism**: The chemiosmotic mechanism for ATP synthesis, proposed by P. Mitchell, explains how ATP is produced in cells, particularly in the mitochondria and chloroplasts. It involves the movement of protons (H⁺ ions) across a membrane.

2. **Role of Water Splitting**: In the process of photosynthesis, water is split (photolysis), producing protons and electrons. The electrons are transferred through the electron transport chain (ETS).

3. **Proton Pumping**: As electrons move through the ETS, they provide energy that is used to pump protons from the inner membrane to the outer membrane. This creates a higher concentration of protons outside the inner membrane compared to the inside.

4. **Creation of Proton Gradient**: The difference in proton concentration across the membrane creates a proton gradient, which is a form of potential energy.

5. **Proton Motive Force**: The energy stored in this proton gradient is referred to as the proton motive force (PMF). It is the driving force for ATP synthesis.

6. **ATP Synthesis**: The enzyme ATP synthase utilizes the proton motive force to synthesize ATP as protons flow back into the inner membrane through ATP synthase.

7. **Conclusion**: Therefore, the factor responsible for ATP synthesis according to the chemiosmotic mechanism is the proton motive force.

**Final Answer**: The factor responsible for ATP synthesis according to the chemiosmotic mechanism is the **proton motive force**.

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