ATP synthesis is linked to

Options

A. Development of water potential gradient across the membrane.
B. Development of H.. gradient across the membrane
C. Reduction of PS I by `NADP^(+)`
D. Oxidation of PS II by `H_2O`

Answer

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

1. **Understanding ATP Synthesis**: ATP synthesis occurs during the process of photosynthesis, particularly in the light-dependent reactions. It is primarily linked to the flow of electrons through the electron transport chain.

2. **Role of Electron Transport**: As electrons are transported through the electron transport chain, they help in the pumping of protons (H⁺ ions) across the thylakoid membrane, creating a proton gradient.

3. **Proton Gradient Formation**: The movement of protons across the membrane creates a difference in concentration (proton gradient) on either side of the membrane. This gradient is crucial for ATP synthesis.

4. **Membrane Potential**: The proton gradient also contributes to the membrane potential, which is the difference in charge across the membrane. This potential energy is harnessed to synthesize ATP.

5. **Identifying the Correct Link**: Among the options provided, the development of the H⁺ gradient across the membrane is directly linked to ATP synthesis. This is because ATP synthase uses the energy from the flow of protons back across the membrane to convert ADP and inorganic phosphate into ATP.

6. **Conclusion**: Therefore, ATP synthesis is linked to the development of the H⁺ gradient across the membrane.

**Final Answer**: ATP synthesis is linked to the development of H⁺ gradient across the membrane.

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