And as this process continually takes place, we build up the amount of ammonia that is present inside our skeleton muscle cells. Now, ammonium is toxic, and so what the skeleton muscle cells must do is they must be able to dispose of that ammonium. Now, unlike in the liver, and to a smaller extent in the kidney, where we have the urea cycle to basically dispose of that ammonium inside the skeleton muscle cells, we don't actually have a way to dispose of ammonium directly. And that's because the urea cycle does not take place inside the muscle. And so our body actually has two ways by which it can get rid of this ammonium from our skeletal muscle. But ultimately, what the skeleton muscle cell must do is it must be able to transport that ammonium back to the liver, where that ammonium can be fed into the urea cycle.