The TCA pathway, also known as the citric acid cycle is a catabolic pathway of aerobic respiration. This pathway generates energy in the cell. The cycle can start from Acetyl-CoA interacting with Oxalacetic acid and water through a citrate synthase monomer resulting in a hydrogen ion, CoA and a Citric Acid. The latter compound is dehydrated by a Citrate hydro-lyase resulting in the release of water and a cis-Aconitic acid. This compound is then hydrated through a Citrate hydro-lyase resulting in a D-threo-Isocitric acid. This compound is decarboxylated by an NADP dependent Citrate dehydrogenase, resulting in a release of carbon dioxide and NADPH and Oxoglutaric acid. The oxoglutaric acid interacts with a Coenzyme A through a NAD driven 2-oxoglutarate dehydrogenase resulting in a release of carbon dioxide, an NADH and succinyl-CoA. The succinyl-CoA interacts with a phosphate and an ADP through a 2-oxoglutarate dehydrogenase resulting in a CoA, an ATP and Succinic Acid. Succinic acid interacts with a ubiquinone, in this case a ubiquinone 1 through a succinate:quinone oxidoreductase resulting in an ubiquinol, in this case a ubiquinol-1 and a fumaric acid. The fumaric acid interacts with water through a fumarase hydratase resulting in a L-Malic acid.This compound can either interact with quinone through a malate:quinone oxidoreductase resulting in a release of hydroquinone and oxalacetic acid, or it can react with an NAD through a malate dehydrogenase resulting in a hydrogen ion, NADH and Oxalacetic acid.

TCA cycle References