So contraction of muscle, it can be skeleton muscle or cardiac muscle or smooth muscle, uses ATP molecules. Now, what types of processes actually make up glucose metabolism? So the first process that we're going to look at will be glycolysis. And glycolysis is the process by which the glucose molecules present in a cytoplasm are broken down into Pyruvate molecules. So two Pyruvate molecules are net result of two ATP molecules which can be used by the cell to carry out some type of process as well as NADH molecules. And we'll discuss what those are in a future lecture.