<Table> Reactions of the urea cycle <Tr> <Th> Step </Th> <Th> Reactants </Th> <Th> Products </Th> <Th> Catalyzed by </Th> <Th> Location </Th> </Tr> <Tr> <Th> </Th> <Td> NH + HCO + 2 ATP </Td> <Td> carbamoyl phosphate + 2 ADP + P </Td> <Td> CPS1 </Td> <Td> mitochondria </Td> </Tr> <Tr> <Th> </Th> <Td> carbamoyl phosphate + ornithine </Td> <Td> citrulline + P </Td> <Td> OTC, zinc, biotin </Td> <Td> mitochondria </Td> </Tr> <Tr> <Th> </Th> <Td> citrulline + aspartate + ATP </Td> <Td> argininosuccinate + AMP + PP </Td> <Td> ASS </Td> <Td> cytosol </Td> </Tr> <Tr> <Th> </Th> <Td> argininosuccinate </Td> <Td> Arg + fumarate </Td> <Td> ASL </Td> <Td> cytosol </Td> </Tr> <Tr> <Th> 5 </Th> <Td> Arg + H O </Td> <Td> ornithine + urea </Td> <Td> ARG1, manganese </Td> <Td> cytosol </Td> </Tr> </Table> <Tr> <Th> Step </Th> <Th> Reactants </Th> <Th> Products </Th> <Th> Catalyzed by </Th> <Th> Location </Th> </Tr> <Tr> <Th> </Th> <Td> NH + HCO + 2 ATP </Td> <Td> carbamoyl phosphate + 2 ADP + P </Td> <Td> CPS1 </Td> <Td> mitochondria </Td> </Tr> <Tr> <Th> </Th> <Td> carbamoyl phosphate + ornithine </Td> <Td> citrulline + P </Td> <Td> OTC, zinc, biotin </Td> <Td> mitochondria </Td> </Tr>

Where do the two nitrogens in urea come from