Chemiosmotic hypothesis is based on

Options

A. Membrane potential
B. Proton gradient
C. Accumulation of `K^(+)` ions
D. Accumulation of `Na^(+)` ions

Answer

**Step-by-Step Solution:**

1. **Understanding the Chemiosmotic Hypothesis**: The chemiosmotic hypothesis explains how ATP (adenosine triphosphate) is produced in cells, particularly during processes like photosynthesis and cellular respiration.

2. **Role of Proton Gradient**: According to the hypothesis, ATP synthesis is driven by a proton (H+) gradient across a membrane. This gradient is created by the movement of protons into the thylakoid lumen of chloroplasts or the inner mitochondrial membrane.

3. **Formation of Electrochemical Gradient**: The accumulation of protons in these compartments leads to the formation of an electrochemical gradient. This gradient consists of two components:
- **Chemical Gradient**: This is due to the difference in concentration of protons (H+) across the membrane.
- **Electrical Gradient**: This arises because protons carry a positive charge, leading to a difference in charge across the membrane.

4. **ATP Generation**: When protons move down their electrochemical gradient (from a region of high concentration to low concentration), they pass through ATP synthase, a protein complex that synthesizes ATP from ADP (adenosine diphosphate) and inorganic phosphate (Pi).

5. **Conclusion**: The chemiosmotic hypothesis is fundamentally based on the establishment and utilization of the proton electrochemical gradient to drive ATP synthesis.

**Final Answer**: The chemiosmotic hypothesis is based on the proton electrochemical gradient.

---