Eventually, we begin to break down the branch chain amino acids into the carbon scale intermediates, and then we form ammonium as a byproduct. Now, ammonium must be transformed into some other molecules. So we must have some type of carrier molecule that ultimately transports through the blood to the liver. So ammonium must be combined with Pyruvate. Now, where do we get the Pyruvate from? Well, inside our muscle, we have glycogen storages.