The enzyme required for `CO_(2)` fixation in Calvin cycle is

Options

A. PEP carboxylase
B. RuBP oxygenase
C. RuBP carboxylase
D. RuP carboxylase

Answer

To answer the question regarding the enzyme required for CO₂ fixation in the Calvin cycle, we can follow these steps:

### Step-by-Step Solution:

1. **Understand the Calvin Cycle**: The Calvin cycle is a series of biochemical reactions that occur in the stroma of chloroplasts in plants. Its primary function is to convert atmospheric carbon dioxide (CO₂) into carbohydrates, which serve as energy sources for the plant.

**Hint**: Remember that the Calvin cycle is essential for photosynthesis and takes place in the chloroplasts.

2. **Identify the Phases of the Calvin Cycle**: The Calvin cycle consists of three main phases: carbon fixation, reduction, and regeneration. The first phase is where CO₂ is fixed into an organic molecule.

**Hint**: Focus on the first phase of the Calvin cycle, which is crucial for CO₂ fixation.

3. **Determine the Enzyme Involved in CO₂ Fixation**: The enzyme responsible for the fixation of CO₂ in the Calvin cycle is known as RuBisCO, which stands for ribulose bisphosphate carboxylase/oxygenase. This enzyme catalyzes the reaction between CO₂ and ribulose bisphosphate (RuBP) to form 3-phosphoglycerate (3-PGA).

**Hint**: Look for the enzyme that facilitates the initial reaction of CO₂ with RuBP.

4. **Evaluate the Given Options**: The options provided are:
- Phosphoenol pyruvate carboxylase
- RuBisCO bisphosphate oxygenase
- RuBisCO bisphosphate carboxylase
- RuBisCO phosphate carboxylase

Among these, the correct option is "RuBisCO bisphosphate carboxylase," which is commonly referred to simply as RuBisCO.

**Hint**: Identify the option that specifically mentions RuBisCO and relates to carboxylation.

5. **Conclude the Answer**: Based on the information and analysis, the enzyme required for CO₂ fixation in the Calvin cycle is **RuBisCO bisphosphate carboxylase**.

**Final Answer**: The enzyme required for CO₂ fixation in the Calvin cycle is **RuBisCO bisphosphate carboxylase** (option number 3).