During photosynthesis oxygen in glucose comes from

Options

A. water
B. carbon dioxide
C. both (1) and (2)
D. oxygen in air

Answer

To answer the question "During photosynthesis, oxygen in glucose comes from," we can follow these steps:

### Step-by-Step Solution:

1. **Understand the Chemical Composition of Glucose**:
- The chemical formula for glucose is C₆H₁₂O₆. This indicates that glucose contains carbon (C), hydrogen (H), and oxygen (O).

2. **Identify the Sources of Oxygen in Photosynthesis**:
- Photosynthesis occurs in two main stages: the light-dependent reactions and the light-independent reactions (Calvin cycle).
- During the light-dependent reactions, water (H₂O) is split in a process called photolysis, which releases oxygen (O₂) as a by-product. However, this oxygen is not part of the glucose molecule.

3. **Focus on the Calvin Cycle**:
- The Calvin cycle (light-independent reactions) uses carbon dioxide (CO₂) from the atmosphere to synthesize glucose.
- In the process of synthesizing glucose, oxygen atoms from carbon dioxide contribute to the oxygen atoms in glucose.

4. **Conclusion**:
- Therefore, the oxygen atoms that are part of the glucose molecule (C₆H₁₂O₆) come from carbon dioxide (CO₂) during the Calvin cycle, not from the water that is split during the light-dependent reactions.

5. **Final Answer**:
- The correct answer to the question is that the oxygen in glucose comes from carbon dioxide (CO₂).