So when we metabolize amino acids and we form that carbon skeleton by removing that alpha amino group, one exactly happens to that carbon skeleton. So all the carbon skeletons that we form, when we metabolize the 20 different types of amino acids inside our liver cells, all those carbon skeletons lead to one of seven different molecules. And all these seven molecules are intermediates of the metabolic pathway, the metabolic system that allows us to generate high energy ATP molecules. So let's recall some basic facts about metabolic pathways. Let's begin with the citric acid cycle. So this is our citric acid cycle.