In photorespiration , the first stable product is

Options

A. oxalo acetate.
B. phosphoglycerate.
C. phosphoglycerate and phosphoglycolate.
D. None of these

Answer

To solve the question about the first stable product formed in photorespiration, we can break down the process step by step.

### Step-by-Step Solution:

1. **Understanding Photorespiration**:
- Photorespiration is a process that occurs primarily in C3 plants when the concentration of oxygen is higher than that of carbon dioxide. It is often considered a wasteful pathway because it does not lead to the production of glucose.

**Hint**: Remember that photorespiration occurs mainly in C3 plants and is triggered by high oxygen levels.

2. **Role of Rubisco**:
- The enzyme ribulose 1,5-bisphosphate carboxylase/oxygenase (commonly known as Rubisco) plays a crucial role in this process. It can catalyze two reactions: one with carbon dioxide (carboxylase activity) and one with oxygen (oxygenase activity).

**Hint**: Rubisco can act on both CO2 and O2, leading to different products based on their concentrations.

3. **Formation of Products**:
- When Rubisco reacts with carbon dioxide, it forms two molecules of 3-phosphoglycerate (3-PGA).
- However, when Rubisco reacts with oxygen (which happens during photorespiration), it produces one molecule of 3-phosphoglycerate and one molecule of phosphoglycolate.

**Hint**: Focus on the products formed when Rubisco acts as an oxygenase.

4. **Identifying the First Stable Product**:
- In the context of photorespiration, the first stable product formed when Rubisco reacts with oxygen is phosphoglycerate (3-PGA). Although phosphoglycolate is also formed, it is not stable and is quickly converted into other compounds.

**Hint**: The term "stable product" refers to the compound that remains longer in the metabolic pathway.

5. **Conclusion**:
- Therefore, the correct answer to the question "In photorespiration, the first stable product is" is **phosphoglycerate (3-PGA)**.

### Final Answer:
The first stable product in photorespiration is **phosphoglycerate (3-PGA)**.