Urea cycle is linked with TCA cycle in three different ways:

1. Production of fumarate in urea cycle is the most important integrative 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 argininosuccinate. Oxaloacetate is an important metabolite which can combine with acetyl CoA to form citrate and get finally oxidised. Oxaloacetate can also serve as a precursor for the synthesis of glucose (gluconeogenesis).
2. ATP (12) is generated in TCA cycle, while ATP (4) is utilised for urea synthesis.
3. Citric acid cycle is an important metabolic pathway for complete oxidation of various metabolites to CO₂ and H₂O. The CO₂ liberated in TCA cycle (in the mitochondria) can be utilised in urea cycle.