Although our liver is responsible for the majority of the metabolism of amino acids that occurs inside our body, other organs and tissues can also break down amino acids and then use the carbon skeleton byproducts for energy. And one example of such a tissue is our muscle tissue. So if we're undergoing prolonged exercise or if we're fasting, our skeleton muscle tissue tissue can actually begin to break down branch chain amino acids such as valine, isolucine and leucine. And then we form carbon skeleton intermediates, and then those are used for energy purposes. But of course, every time we metabolize amino acids, we form nitrogen as a byproduct. More specifically, we form ammonium.