First transitory chemical formed by reaction between `CO_(2)` and RuBP is

Options

A. `PGAL//GAP`
B. `PGA`
C. 2-carboxy 3-keto, 1, 5-bisphosphoribotol
D. `DiHAP`.

Answer

To determine the first transitory chemical formed by the reaction between carbon dioxide (CO₂) and ribulose 1,5-bisphosphate (RuBP) in the Calvin cycle, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding the Calvin Cycle**:
The Calvin cycle is a series of biochemical reactions that take place in the chloroplasts of photosynthetic organisms. It is responsible for the fixation of carbon dioxide and the production of glucose.

2. **Identify the Reactants**:
The primary reactants in the first step of the Calvin cycle are carbon dioxide (CO₂) and ribulose 1,5-bisphosphate (RuBP).

3. **Role of Rubisco**:
The enzyme ribulose bisphosphate carboxylase/oxygenase (commonly known as Rubisco) catalyzes the reaction between CO₂ and RuBP.

4. **Formation of Transitory Compound**:
When CO₂ reacts with RuBP in the presence of Rubisco, an unstable intermediate compound is formed. This compound is known as a transitory or unstable chemical.

5. **Identify the Transitory Compound**:
The unstable intermediate formed is specifically referred to as 2-carboxy-3-keto-1,5-bisphosphoribulose. This compound is short-lived and quickly breaks down.

6. **Splitting of the Transitory Compound**:
The unstable intermediate (2-carboxy-3-keto-1,5-bisphosphoribulose) rapidly undergoes hydrolysis (reaction with water) to produce two molecules of phosphoglyceric acid (PGA), which is the first stable product of the Calvin cycle.

7. **Conclusion**:
Therefore, the first transitory chemical formed by the reaction between CO₂ and RuBP is **2-carboxy-3-keto-1,5-bisphosphoribulose**.

### Final Answer:
The first transitory chemical formed by the reaction between CO₂ and RuBP is **2-carboxy-3-keto-1,5-bisphosphoribulose**.

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