Primary link between citric acid cycle and urea cycle with

(Fumarate): (340-U.Satyanarayan 3rd) (145-Harper 28th)Integration between Urea cycle and Citric acid cycleUrea cycle is linked with citric acid cycle (TCA cycle) in three different ways. This is regarded as bicyclic integration between the two cycle1. The production of fumarate in urea cycle is the most important integrating point with TCA cycle fumarate is converted to malate and then to oxaloacetate in TCA cycle. Oxaloacetate undergoes transamination to produce aspartate which enters urea cycle. Here it combines with citrulline to produce arginosuccinate. Oxaloacetate is an important metabolite which can combine with acetyl COA to form citrate and get finally oxidized. Oxaloacetate can also serve as precursor for the synthesis of glucose (gluconeogenesis)2. ATP (12) are generated in the TCA cycle while ATP (4) are utilized for the urea synthesis3. Citric acid cycle is an important metabolic pathway for the complete oxidation of various metabolites to CO2 and H2O. The CO2 liberated in TCA cycle (in the mitochondria) can be utilized in urea cycle.