Now, there are two major pathways. We have an aerobic pathway and an anaerobic pathway. Now, in aerobic, that simply means we're going to use oxygen. And in this particular case, the pyruvate molecules travel into the mitochondria and there they're broken down into acetylcoenzyme A. And that molecule goes into the citric acid cycle and that uses the electron transport chain to basically regenerate those NAD plus molecules. But we'll focus on that process in a future lecture.