`NADP^(+)` is reduced to NADPH in

Options

A. PS-I
B. PS-II
C. Calvin cycle
D. Non-cyclic photophosphorylation

Explanation

**Step-by-Step Solution:**

1. **Understanding the Role of NADP+**: NADP+ (Nicotinamide adenine dinucleotide phosphate) acts as an electron carrier in the process of photosynthesis. It is essential for the conversion of light energy into chemical energy.

2. **Identifying the Process**: NADP+ is reduced to NADPH during the light-dependent reactions of photosynthesis. This occurs specifically in the process known as non-cyclic photophosphorylation.

3. **Mechanism of Reduction**:
- In non-cyclic photophosphorylation, light energy is absorbed by photosystem II (PSII), which excites electrons.
- These excited electrons are transferred to a primary electron acceptor and then move through a series of proteins, including plastoquinone and the cytochrome complex, ultimately reaching photosystem I (PSI).
- In PSI, the electrons are again excited by light energy and are transferred to another primary acceptor.

4. **Formation of NADPH**:
- The electrons from PSI are transferred to ferredoxin, which then passes them to the enzyme NADP+ reductase.
- NADP+ reductase catalyzes the reduction of NADP+ to NADPH by adding electrons and protons (H+ ions).

5. **Source of Protons (H+)**: The protons required for the reduction of NADP+ to NADPH come from the splitting of water molecules (photolysis) during the light reactions. This process also releases oxygen as a byproduct.

6. **Conclusion**: Therefore, the reduction of NADP+ to NADPH occurs in the process of non-cyclic photophosphorylation during the light-dependent reactions of photosynthesis.

**Final Answer**: NADP+ is reduced to NADPH in non-cyclic photophosphorylation.

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