The most common pathway for glucose (as well as fructose and mannose) catabolism is glycolysis, and the main purpose of this pathway under anaerobic conditions is energy production. It is noteworthy that when cells capable of fermentation like S. cerevisiae become anaerobic, the rate of glycolysis speeds up 10 times or more (Purves et al., 2001), so a growth-sustaining level of energy generation is achieved despite the low yield of ATP generated by the metabolism of glucose through this pathway. During glycolysis, parts of the original glucose carbon skeleton will also be used for biomass formation or anabolism (the synthesis of biological molecules, amino acids, nucleic acids, lipids etc., according to the need of the growing and multiplying cells). The glycolytic pathway (or glycolysis) (Figure 2.2.2), the conversion of glucose to pyruvate, is a universal pathway for glucose catabolism that is encountered throughout the eukaryotic kingdom, as well as in many