First reduction in pentose phosphate pathway is

Options

A. Oxidation of 6-phosphogluconate
B. Oxidation of fructose 6-phosphate
C. Oxidation of glucose 6-phosphate
D. Oxidation of fructose 5-phosphate.

Answer

### Step-by-Step Text Solution

1. **Understanding the Pentose Phosphate Pathway (PPP)**:
- The pentose phosphate pathway is a metabolic pathway parallel to glycolysis. It is primarily involved in the oxidation of glucose-6-phosphate and the production of NADPH and ribose-5-phosphate.

2. **Identifying the First Step**:
- The first step in the pentose phosphate pathway involves the oxidation of glucose-6-phosphate. This step is crucial as it leads to the formation of 6-phosphogluconate.

3. **Reduction and Oxidation**:
- In the context of the PPP, the term "reduction" refers to the conversion of glucose-6-phosphate to 6-phosphogluconate. This process involves the reduction of NADP+ to NADPH, which is a key product of the pathway.

4. **Conclusion**:
- Therefore, the first reduction in the pentose phosphate pathway is the oxidation of glucose-6-phosphate to 6-phosphogluconate.

5. **Final Answer**:
- The correct option for the first reduction in the pentose phosphate pathway is the oxidation of glucose-6-phosphate.