Connecting link betwee glycolysis and Krebs cycle is/before entering Krebs cycle pyruvate is changed to

Options

A. Oxaloacetate
B. PEP
C. Pyruvate
D. Acetyl CoA.

Explanation

To solve the question about the connecting link between glycolysis and the Krebs cycle, we will follow these steps:

### Step-by-Step Solution:

1. **Understanding Glycolysis**: Glycolysis is the process that breaks down glucose into two molecules of pyruvate. This occurs in the cytoplasm of the cell and produces a small amount of ATP and NADH.

2. **Identifying the Link Reaction**: Before pyruvate can enter the Krebs cycle, it must undergo a transformation. This transformation is known as the link reaction or the transition reaction, which connects glycolysis to the Krebs cycle.

3. **Location of the Link Reaction**: The link reaction occurs in the mitochondrial matrix, where the pyruvate produced from glycolysis is transported.

4. **Conversion of Pyruvate**: In the link reaction, each pyruvate (which is a three-carbon molecule) is converted into acetyl coenzyme A (acetyl CoA), which is a two-carbon molecule. This conversion involves the removal of one carbon atom from pyruvate, which is released as carbon dioxide (CO₂).

5. **Role of Enzymes and Coenzymes**: The enzyme responsible for this conversion is called pyruvate dehydrogenase. During this reaction, NAD⁺ is reduced to NADH, and coenzyme A (CoA) is added to the acetyl group, forming acetyl CoA.

6. **Final Product**: The final product of this link reaction is acetyl coenzyme A (acetyl CoA), which then enters the Krebs cycle by combining with oxaloacetic acid to form citric acid, the first stable product of the Krebs cycle.

7. **Conclusion**: Therefore, the connecting link between glycolysis and the Krebs cycle is the conversion of pyruvate into acetyl coenzyme A.

### Final Answer:
The connecting link between glycolysis and the Krebs cycle is the conversion of pyruvate into **acetyl coenzyme A**.

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