During non cyclic-photophosphorylation, water is oxidized and the electrons from water pass through PSII and PSI before reducing :

Options

A. Carbon dioxide
B. NADP
C. Plastoquinone
D. RuBP carboxylase

Answer

**Step-by-Step Solution:**

1. **Understanding Non-Cyclic Photophosphorylation**: Non-cyclic photophosphorylation is a process that occurs in the thylakoid membranes of chloroplasts during photosynthesis. It involves the conversion of light energy into chemical energy in the form of ATP and NADPH.

2. **Oxidation of Water**: During this process, water (H₂O) is oxidized. This means that water molecules are split into oxygen (O₂), protons (H⁺), and electrons (e⁻). The reaction can be summarized as:
\[ 2 H_2O \rightarrow 4 H^+ + 4 e^- + O_2 \]

3. **Electron Transport Chain**: The electrons released from the oxidation of water are transferred through a series of proteins in the thylakoid membrane. The first complex they encounter is Photosystem II (PSII), which contains a special pair of chlorophyll molecules known as P680.

4. **Movement to Photosystem I**: After being energized by light, the electrons are transferred from PSII to plastoquinone and then to the cytochrome b6f complex, and finally to Photosystem I (PSI), which contains P700.

5. **Reduction of NADP⁺**: Once the electrons reach PSI, they are again energized by light and are then used to reduce NADP⁺ to NADPH. This reduction process is crucial as NADPH serves as a reducing agent in the Calvin cycle.

6. **Final Products**: The overall products of non-cyclic photophosphorylation include ATP, NADPH, and O₂. The question specifically asks for what happens before the reduction of NADP⁺, which is the production of NADPH itself.

7. **Conclusion**: Therefore, the electrons from water pass through PSII and PSI before reducing NADP⁺ to NADPH.

**Final Answer**: The electrons from water pass through PSII and PSI before reducing NADP⁺.

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