Page "Biochemistry" Paragraph 33

Glucose 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 < sup >+</ sup > to NADH.

This does not require oxygen ; if no oxygen is available ( or the cell cannot use oxygen ), the NAD is restored by converting the pyruvate to lactate ( lactic acid ) ( e. g., in humans ) or to ethanol plus carbon dioxide ( e. g., in yeast ).

Other monosaccharides like galactose and fructose can be converted into intermediates of the glycolytic pathway.