And in step five, what we ultimately want to do here is we want to remove this group here. We want to attach an oxygen to form that urea and the resulting carbon skeleton that is formed is that ornithine amino acid that ultimately goes back into the matrix and is reused to continue this urea cycle. And so the enzyme arginase uses a water molecule to essentially attack and hydrolyze this bond here, breaking this bond, forming the ornithine as well as that urea. And so we see the oxygen came from this water. In step five, the carbon came from the bicarbonate. In step one, this nitrogen came from step three, that aspartate.