is mainly metabolized by a very important ten-step pathway called glycolysis, the net result of which is to break down one molecule of glucose into two molecules of pyruvate; this also produces a net two molecules of ATP, the energy currency of cells, along with two reducing equivalents in the form of converting NAD+ to NADH. This does not require oxygen; if no oxygen is available, the NAD is restored by converting the pyruvate to lactate or to ethanol plus carbon dioxide. Other monosaccharides like galactose and fructose can be converted into intermediates of the glycolytic pathway.