During the conversion of succinyl CoA to succinic acid needs GDP + Pi which converted to GTP. So the correct option is 'GDP + Pi (ie)GTP

The correct answer for the conversion of succinyl-CoA to succinic acid in the Krebs cycle is option 'A', which is GTP.

The Krebs cycle, also known as the citric acid cycle or the tricarboxylic acid cycle, is a series of chemical reactions that occur in the mitochondria of cells. It plays a crucial role in the production of energy through the oxidation of acetyl-CoA, which is derived from various sources such as carbohydrates, fats, and proteins.

Here is a detailed explanation of the conversion of succinyl-CoA to succinic acid in the Krebs cycle:

1. Formation of Succinyl-CoA:
- The Krebs cycle begins with the condensation of acetyl-CoA and oxaloacetate, catalyzed by the enzyme citrate synthase, to form citrate.
- Citrate undergoes a series of enzymatic reactions, resulting in the conversion of isocitrate to alpha-ketoglutarate.
- Alpha-ketoglutarate is further oxidized to form succinyl-CoA, with the help of the enzyme alpha-ketoglutarate dehydrogenase complex.

2. Conversion of Succinyl-CoA to Succinic Acid:
- The conversion of succinyl-CoA to succinic acid involves the transfer of a phosphate group from succinyl-CoA to a nucleotide diphosphate, forming either GTP or ATP.
- In this specific reaction, the enzyme succinyl-CoA synthetase catalyzes the conversion of succinyl-CoA to succinic acid, with the simultaneous synthesis of GTP.
- GTP, or guanosine triphosphate, is a high-energy molecule, similar to ATP, that can be utilized by cells for various energy-requiring processes.

Therefore, in the Krebs cycle, the conversion of succinyl-CoA to succinic acid is accompanied by the synthesis of GTP. This GTP can later be used to generate ATP through the process of substrate-level phosphorylation, where the high-energy phosphate bond of GTP is transferred to ADP to form ATP.

In summary, option 'A' (GTP) is the correct answer for the conversion of succinyl-CoA to succinic acid in the Krebs cycle. GTP is synthesized during this step and can be used to produce ATP, providing energy for cellular processes.