The substrate in Krebs cycle which undergoes a reaction very similar to pyruvic acid in mitochondria is

Options

A. aconitate
B. succinic acid
C. alpha - ketoglutaric acid
D. fumaric acid

Answer

To solve the question regarding the substrate in the Krebs cycle that undergoes a reaction similar to pyruvic acid in mitochondria, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding Pyruvic Acid**:
- Pyruvic acid is the end product of glycolysis and enters the mitochondria for further processing.

2. **Identifying the Reaction**:
- In the mitochondria, pyruvic acid undergoes a process called oxidative decarboxylation. This process involves the removal of a carbon dioxide molecule and the conversion of pyruvic acid into acetyl coenzyme A (acetyl-CoA).

3. **Key Components of the Reaction**:
- The reaction requires:
- NAD+ (which gets reduced to NADH)
- Coenzyme A (CoA)
- The enzyme pyruvate dehydrogenase
- Magnesium ions as an activator.

4. **Finding a Similar Reaction in the Krebs Cycle**:
- In the Krebs cycle, a similar reaction occurs with alpha-ketoglutaric acid.
- Alpha-ketoglutaric acid also undergoes oxidative decarboxylation, resulting in the formation of succinyl coenzyme A.

5. **Components of the Alpha-Ketoglutaric Acid Reaction**:
- This reaction also requires:
- NAD+ (which is reduced to NADH)
- Coenzyme A
- The enzyme alpha-ketoglutarate dehydrogenase
- Thiamine pyrophosphate, lipoic acid, and magnesium ions as activators.

6. **Conclusion**:
- Since both pyruvic acid and alpha-ketoglutaric acid undergo similar reactions involving oxidative decarboxylation, the substrate in the Krebs cycle that undergoes a reaction very similar to pyruvic acid is **alpha-ketoglutaric acid**.

### Final Answer:
The substrate in the Krebs cycle which undergoes a reaction very similar to pyruvic acid in mitochondria is **alpha-ketoglutaric acid**.

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