In CAM pathway the first dicarboxylic acid is formed as resultant of

Options

A. Night `CO_2` fixation
B. Decarboxylation of malic acid
C. Second `CO_2` fixation
D. Phosphorylation of pyruvic acid

Answer

### Step-by-Step Solution:

1. **Understanding the CAM Pathway**:
- The Crassulacean Acid Metabolism (CAM) pathway is a photosynthetic process used by certain plants to fix carbon dioxide (CO2) at night to minimize water loss during the day.

2. **Identifying the First Dicarboxylic Acid**:
- In the CAM pathway, the first dicarboxylic acid formed is a result of the initial fixation of CO2.

3. **CO2 Fixation at Night**:
- During the night, CO2 is fixed into a 3-carbon molecule called phosphoenolpyruvate (PEP). This reaction is catalyzed by the enzyme PEP carboxylase.

4. **Formation of Oxaloacetic Acid (OAA)**:
- The CO2 combines with PEP to form oxaloacetic acid (OAA), which is a 4-carbon dicarboxylic acid.

5. **Conclusion**:
- Therefore, the first dicarboxylic acid formed in the CAM pathway is oxaloacetic acid (OAA), resulting from the nighttime fixation of CO2.

### Final Answer:
The first dicarboxylic acid formed in the CAM pathway is oxaloacetic acid (OAA) as a result of nighttime CO2 fixation.

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