In hexose monophosphate shunt, glucose 6-phosphate undergoes

Options

A. One dehydrogenation and one decarboxylation
B. Two dehydrogenations and one decarboxylation
C. Two dehydrogenations and two decarboxylations
D. Two dehydrogenations and three decarboxylations.

Answer

**Step-by-Step Solution:**

1. **Understanding the Hexose Monophosphate Shunt:**
The hexose monophosphate shunt, also known as the pentose phosphate pathway (PPP), is a metabolic pathway parallel to glycolysis. It primarily serves to generate NADPH and ribose-5-phosphate for nucleotide synthesis.

2. **Initial Conversion:**
The pathway begins with glucose 6-phosphate, which is derived from glucose. Instead of entering glycolysis, glucose 6-phosphate is converted into 6-phosphogluconate.

3. **First Reaction - Dehydrogenation:**
The conversion of glucose 6-phosphate to 6-phosphogluconate is catalyzed by the enzyme glucose 6-phosphate dehydrogenase. During this reaction, NADP+ is reduced to NADPH. This step is classified as a dehydrogenation reaction because it involves the removal of hydrogen.

4. **Second Reaction - Dehydrogenation and Decarboxylation:**
Next, 6-phosphogluconate is converted to ribulose 5-phosphate. This reaction is catalyzed by the enzyme 6-phosphogluconate dehydrogenase. In this step, another dehydrogenation occurs (NADP+ is again reduced to NADPH), and decarboxylation takes place, releasing carbon dioxide (CO2).

5. **Summary of Reactions:**
- Total dehydrogenation reactions: 2 (one from glucose 6-phosphate to 6-phosphogluconate and one from 6-phosphogluconate to ribulose 5-phosphate).
- Total decarboxylation reactions: 1 (from 6-phosphogluconate to ribulose 5-phosphate).

6. **Conclusion:**
Therefore, in the hexose monophosphate shunt, glucose 6-phosphate undergoes a total of 2 dehydrogenations and 1 decarboxylation.

**Final Answer:**
In the hexose monophosphate shunt, glucose 6-phosphate undergoes 2 dehydrogenations and 1 decarboxylation.

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