Carbamoyl group of carbamoyl phosphate is derived from ?

Ans. is 'a' i.e., Ammonia 1st reaction of urea cycle is synthesis of carbamoyl phosphate by condensation of ammonia (NH4') and CO2.The carbamoyl group of carbomoyl phosphate is derived from NH4. and a bicarbonate ion.The reaction is energetically demanding (two ATP) and is catalyzed by carbomoyl phosphate synthase LCPS-I is allosterically activated by N-acetyl glutamate.