prokaryotes. This pathway is active under both fermentative and respiratory metabolism. Glycolysis consists of 10 steps, each catalyzed by a specific enzyme. The carbon skeleton of the sugar molecule is gradually dismembered during this process, and energy from the bond breaking is harvested in the form of ATP from ADP, and NADH from NAD+. The first steps in glycolysis require an input of energy in the form of ATP, and serve to reorganize the sugar molecule. In fact, energy is invested in the first five reactions of glycolysis, and harvested in reactions 6, 7 and 10 (Jackson, 2000c). In step 4, the six-carbon sugar is split into two three-carbon moieties (glyceraldehydes and dihydroxyacetone) by the enzyme aldolase, and the preparatory reactions are complete. Thereafter, dihydroxyacetone is converted to glyceraldehydes and the two glyceraldehydes molecules are oxidized (hydrogen atoms with their electrons are removed), in the process reducing NAD+ is to NADH. High energy bonds formed during glycolysis between phosphate groups and the substrate molecules are gradually broken, and the phosphate groups transferred to ADP molecules to form ATP.