Number of dehydrogenation in pentose phosphate pathways is

Options

A. 2
B. 1
C. 3
D. 4

Answer

### Step-by-Step Solution:

1. **Understanding the Pentose Phosphate Pathway (PPP)**:
- The Pentose Phosphate Pathway is a metabolic pathway parallel to glycolysis. It is crucial for producing NADPH and ribose-5-phosphate.

2. **Identifying Dehydrogenation Reactions**:
- Dehydrogenation refers to the removal of hydrogen atoms from a substrate, which typically involves the reduction of NADP+ to NADPH.

3. **First Dehydrogenation**:
- The first dehydrogenation occurs when glucose-6-phosphate is converted to 6-phospho-glucono-lactone.
- This reaction is catalyzed by the enzyme **glucose-6-phosphate dehydrogenase**.
- During this process, NADP+ is reduced to NADPH.

4. **Second Dehydrogenation**:
- The second dehydrogenation occurs when 6-phosphogluconate is converted to ribulose-5-phosphate.
- This reaction is catalyzed by the enzyme **6-phosphogluconate dehydrogenase**.
- Similar to the first reaction, NADP+ is again reduced to NADPH.

5. **Conclusion**:
- In total, there are **two dehydrogenation reactions** in the Pentose Phosphate Pathway.

### Final Answer:
The number of dehydrogenation reactions in the Pentose Phosphate Pathway is **2**.

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