During dark reaction of photosynthesis

Options

A. 6 - c sugar is broken down into 3 - c sugar
B. Photolysis of water occurs
C. `CO_2` is reduced to organic compounds
D. `NADP^+` is reduced

Answer

**Step-by-Step Solution:**

1. **Understanding Photosynthesis Phases**: Photosynthesis consists of two main phases: the light reaction and the dark reaction (Calvin Cycle). The light reaction occurs in the thylakoid membranes of the chloroplasts, while the dark reaction occurs in the stroma.

2. **Light Reaction**: During the light reaction, water (H2O) undergoes photolysis, which means it is split into oxygen (O2), protons, and electrons. This process releases oxygen as a byproduct and generates energy carriers like ATP and NADPH.

3. **Dark Reaction (Calvin Cycle)**: The dark reaction does not require light directly but uses the ATP and NADPH produced in the light reaction. The main function of the dark reaction is to fix carbon dioxide (CO2) from the atmosphere and reduce it to form organic compounds, primarily glucose.

4. **Analyzing the Options**:
- **Option A**: "6 C sugar is broken down into 3 C sugar" - This is incorrect as the dark reaction builds up sugars rather than breaking them down.
- **Option B**: "Photolysis of water occurs" - This occurs during the light reaction, not the dark reaction.
- **Option C**: "CO2 is reduced to organic compounds" - This is correct as it describes the primary function of the dark reaction.
- **Option D**: "NADP+ is reduced" - While NADP+ is reduced during the light reaction to form NADPH, this statement does not accurately describe the dark reaction.

5. **Conclusion**: Based on the analysis, the correct answer is **Option C**: CO2 is reduced to organic compounds.

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