The oxygenase activity of Rubisco allows `O_(2)` to compete with `CO_(2)` for combining with

Options

A. PEP
B. OAA
C. RuBP
D. PGA

Answer

### Step-by-Step Solution:

1. **Understanding the Role of RuBisCO**:
- RuBisCO, or Ribulose-1,5-bisphosphate carboxylase/oxygenase, is an enzyme that plays a crucial role in the process of photosynthesis. It facilitates the fixation of carbon dioxide (CO2) in the Calvin Cycle.

2. **Dual Activity of RuBisCO**:
- RuBisCO has two main activities: carboxylase and oxygenase.
- The carboxylase activity allows RuBisCO to combine with CO2, while the oxygenase activity allows it to combine with O2.

3. **Competition Between O2 and CO2**:
- In the presence of both oxygen and carbon dioxide, O2 competes with CO2 for binding to RuBisCO.
- When RuBisCO binds with O2, it leads to a different set of products compared to when it binds with CO2.

4. **Substrates Involved**:
- The primary substrate that RuBisCO combines with is Ribulose-1,5-bisphosphate (RuBP).
- When RuBisCO binds with CO2, it forms 3-phosphoglycerate (PGA). However, when it binds with O2, it produces one molecule of PGA and one molecule of phosphoglycolate.

5. **Conclusion**:
- Therefore, the oxygenase activity of RuBisCO allows O2 to compete with CO2 for combining with RuBP, leading to the formation of different products based on which molecule is bound.

### Final Answer:
The oxygenase activity of RuBisCO allows O2 to compete with CO2 for combining with **Ribulose-1,5-bisphosphate (RuBP)**.

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