What is kreb cycle

• Kreb’s cycle takes place in the mitochondrial matrix.
• Several intermediate compounds are formed, which contain three carboxylic groups and therefore the process is called as tricarboxylic acid cycle (TCA).
• First, the condensation of acetyl group with oxaloacetic acid (OAA) and water takes place to yield citric acid, catalysed by the enzyme citrate synthase and a molecule of CoA is released.
• Citrate is then isomerised to isocitrate, which is followed by two successive steps of decarboxylation, leading to the formation of α-ketoglutaric acid and then succinyl-CoA.
• Succinyl-CoA is oxidised to OAA allowing the cycle to continue and during the conversion of succinyl-CoA to succinic acid a molecule of GTP is synthesised.
• In a coupled reaction, GTP is converted to GDP with the simultaneous synthesis of ATP from ADP.

Pyruvic acid + 4 NAD⁺ + FAD⁺ + 2H₂O + ADP + Pi à 3CO₂ + 4NADH + 4H⁺ + FADH₂ + ATP

• During the process, 8NADH₂, 2FADH₂, 2 GTPs are formed.