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 determine during which reaction in the TCA (Tricarboxylic Acid) cycle GTP is formed, we can analyze the steps of the cycle and identify where GTP synthesis occurs.

### Step-by-Step Solution:

1. **Understanding the TCA Cycle**: The TCA cycle, also known as the Krebs cycle or citric acid cycle, involves a series of chemical reactions used by all aerobic organisms to generate energy.

2. **Identifying Key Reactions**: The TCA cycle includes several key reactions:
- Conversion of Citrate to α-Ketoglutarate
- Conversion of α-Ketoglutarate to Succinyl CoA
- Conversion of Succinyl CoA to Succinate
- Conversion of Succinate to Fumarate
- Conversion of Fumarate to Malate
- Conversion of Malate to Oxaloacetate

3. **Focusing on GTP Formation**: GTP (Guanosine Triphosphate) is formed during the conversion of Succinyl CoA to Succinate. This reaction is a substrate-level phosphorylation where the energy released from the conversion is used to convert GDP (Guanosine Diphosphate) to GTP.

4. **Conclusion**: Therefore, the correct answer to the question is that GTP is formed during the reaction where Succinyl CoA is converted into Succinate.

### Final Answer:
GTP is formed during the conversion of Succinyl CoA to Succinate in the TCA cycle.

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