We remove that urea and we also form the ornithine, the amino acid that ultimately is recycled back into the matrix of mitochondria to ultimately help this cycle continue taking place. So if we look on this molecule, the oxygen shown in blue came from the water. This carbon came from this carbon dioxide. This nitrogen here came from the aspartate and this nitrogen came from this free ammonium. So once we formed the urea, it then moves via the bloodstream to our kidneys and the kidneys ultimately excrete that via urine. Now, let's actually look at the details of each one of these steps and let's begin with step number one.