Which of the following is a direct oxidation pathway being performed by shunting of glycolysis?

Options

A. TCA cycle
B. HMP pathway
C. Direct oxidation pathway
D. Both (2) and (3)

Answer

To solve the question "Which of the following is a direct oxidation pathway being performed by shunting of glycolysis?", we can follow these steps:

### Step-by-Step Solution:

1. **Understand the Question**: The question asks for a direct oxidation pathway that occurs as a diversion or shunting from glycolysis. This means we need to identify pathways that can bypass glycolysis while still performing oxidation.

2. **Analyze the Options**: The options provided include:
- TCA Cycle
- HMP Pathway (also known as Pentose Phosphate Pathway)
- Direct Oxidation Pathway
- Both 2nd and 3rd options

3. **Evaluate the TCA Cycle**: The TCA Cycle (Krebs Cycle) primarily deals with the oxidation of acetyl-CoA derived from pyruvate after glycolysis. Since it does not directly shunt glycolysis, we can eliminate this option.

4. **Evaluate the HMP Pathway**: The HMP pathway (Pentose Phosphate Pathway) is known for producing NADPH and 5-carbon sugars. It can produce glycolytic intermediates like Glyceraldehyde-3-Phosphate and Fructose-6-Phosphate, which can directly feed into glycolysis. This pathway represents a direct oxidation process that shunts glycolysis, making it a valid option.

5. **Evaluate the Direct Oxidation Pathway**: The term "Direct Oxidation Pathway" is somewhat ambiguous but can refer to pathways like the HMP pathway that perform direct oxidation. Thus, this option is also correct.

6. **Combine the Findings**: Since both the HMP pathway and the concept of a direct oxidation pathway are valid in the context of the question, we conclude that the best answer is the last option, which states "both 2nd and 3rd".

### Final Answer:
The correct answer is **option 4: both 2nd and 3rd**.

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