The common molecule between the Kreb cycle and `C_(4)` pathway is

Options

A. Phosphoenolpyruvate
B. Ribulose 1, 5-diphosphate
C. Oxalo-acetic acid
D. Phosphoglyceric acid

Answer

To solve the question regarding the common molecule between the Krebs cycle and the C4 pathway, we can follow these steps:

### Step-by-Step Solution:

1. **Understand the Krebs Cycle**:
- The Krebs cycle, also known as the TCA cycle or citric acid cycle, is a key metabolic pathway that occurs in the mitochondria. It plays a crucial role in cellular respiration, where acetyl-CoA is oxidized to produce energy in the form of ATP, NADH, and FADH2.

2. **Understand the C4 Pathway**:
- The C4 pathway is a photosynthetic process that occurs in certain plants (C4 plants). It involves the fixation of carbon dioxide into a four-carbon compound, which is then used in the Calvin cycle. The C4 pathway helps in efficiently capturing carbon dioxide in conditions of low CO2 concentration and high temperatures.

3. **Identify the Options**:
- The options provided are:
- A) Phosphoenolpyruvate
- B) Ribulose 1,5-diphosphate
- C) Oxaloacetic acid
- D) Phosphoglyceric acid

4. **Analyze Each Option**:
- **Phosphoenolpyruvate**: This is an intermediate in glycolysis, not directly related to either pathway.
- **Ribulose 1,5-diphosphate**: This is the starting compound for the Calvin cycle (C3 pathway), not the C4 pathway.
- **Oxaloacetic acid**: This is a key compound in both the Krebs cycle (where it is formed from acetyl-CoA) and the C4 pathway (where it is the first stable compound formed after CO2 fixation).
- **Phosphoglyceric acid**: This is also an intermediate in glycolysis and not relevant to the question.

5. **Conclusion**:
- The common molecule between the Krebs cycle and the C4 pathway is **Oxaloacetic acid**.

### Final Answer:
**Oxaloacetic acid** is the common molecule between the Krebs cycle and the C4 pathway.