Class 11 Biology Respiration In Plants Tricarboxylic acid cycle

Tricarboxylic acid 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.

Class_11_Biology_Respiration_In_Plants_Krebs_Cycle

Fig. Krebs cycle

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