First reaction in pentose phosphate pathway is

Options

A. Oxidation of glucose-6-phosphate
B. 6-phospogluconic acid
C. Ribose-5-phosphate
D. Fructose-5-phosphate

Answer

### Step-by-Step Solution:

1. **Understanding the Pentose Phosphate Pathway (PPP)**:
- The pentose phosphate pathway is a metabolic pathway that runs parallel to glycolysis. It is primarily involved in anabolic processes, meaning it helps in building molecules rather than breaking them down.

2. **Location of the Pathway**:
- The pentose phosphate pathway occurs in the cytosol (cytoplasm) of the cell, similar to glycolysis.

3. **Key Products of the Pathway**:
- The two main products generated from the pentose phosphate pathway are:
- Ribose 5-phosphate: This sugar is essential for the synthesis of nucleotides, which are the building blocks of DNA and RNA.
- NADPH: This molecule plays a crucial role in various biosynthetic reactions and helps in the building of other molecules.

4. **First Reaction of the Pathway**:
- The first reaction in the pentose phosphate pathway involves the oxidation of glucose 6-phosphate. This is a key step that initiates the pathway and leads to the production of the aforementioned products.

5. **Final Answer**:
- Therefore, the first reaction in the pentose phosphate pathway is the oxidation of glucose 6-phosphate.