Kreb's cycle was discovered by Krebs in pigeon muscles in 1940. Which step is called gateway step. Link reaction/transition reaction in respiration.

Options

A. Glycolysis
B. Formation of acetyl Co-A
C. Citric acid formation
D. ETS Terminal oxidation

Answer

**Step-by-Step Solution:**

1. **Understanding the Krebs Cycle**: The Krebs cycle, also known as the citric acid cycle or TCA cycle, is a series of biochemical reactions that are crucial for cellular respiration. It was discovered by Hans Krebs in pigeon muscles in 1940.

2. **Identifying the Gateway Step**: The question asks for the step referred to as the "gateway step" in respiration. This step is also known as the link reaction or transition reaction.

3. **Formation of Acetyl-CoA**: Before entering the Krebs cycle, glucose (a 6-carbon molecule) is broken down through glycolysis into pyruvate (a 3-carbon molecule). This pyruvate is then oxidized to form acetyl-CoA (a 2-carbon molecule). This conversion occurs in the mitochondria and is essential for the Krebs cycle to proceed.

4. **Significance of Acetyl-CoA**: Acetyl-CoA is the molecule that enters the Krebs cycle, making it the critical link between glycolysis and the Krebs cycle. Therefore, the formation of acetyl-CoA is considered the gateway step in respiration.

5. **Conclusion**: The correct answer to the question is that the formation of acetyl-CoA is the gateway step or link reaction in respiration.

**Final Answer**: The gateway step is the formation of acetyl-CoA.

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