In the TCA cycle, GTP is formed during which of these reactions:

Options

A. Citric acid `to` alpha-ketoglutaric acid
B. Malic acid `to` oxalo-acetic acid
C. alpha - ketaglutaric acid `to` Succinyl Co A
D. Succinyl-Co A `to` Succinic acid

Answer

To solve the question regarding the formation of GTP in the TCA cycle, we will analyze the reactions involved in the cycle step by step.

### Step-by-Step Solution:

1. **Understanding the TCA Cycle**: The TCA cycle, also known as the Krebs cycle or citric acid cycle, is a series of chemical reactions that occur in aerobic organisms to release stored energy through the oxidation of acetyl coenzyme A.

2. **Identifying the Reactions**: The question provides four different reactions that occur in the TCA cycle:
- Reaction 1: Citric acid to alpha-ketoglutaric acid
- Reaction 2: Malic acid to oxaloacetic acid
- Reaction 3: Alpha-ketoglutaric acid to succinyl coenzyme
- Reaction 4: Succinyl coenzyme to succinic acid

3. **Analyzing Each Reaction**:
- **Reaction 1**: Citric acid to alpha-ketoglutaric acid involves the release of CO2 and the formation of NADH, but no GTP is produced.
- **Reaction 2**: Malic acid to oxaloacetic acid also produces NADH, but does not produce GTP.
- **Reaction 3**: Alpha-ketoglutaric acid to succinyl coenzyme produces NADH and CO2, but does not produce GTP.
- **Reaction 4**: Succinyl coenzyme to succinic acid is the reaction where GTP is produced. This reaction involves the conversion of succinyl coenzyme A to succinate, and during this process, one molecule of GTP is formed.

4. **Conclusion**: Based on the analysis, the correct answer to the question is that GTP is formed during the reaction where succinyl coenzyme is converted to succinic acid.

### Final Answer:
GTP is formed during the reaction of succinyl coenzyme to succinic acid.

---