atp
Steps in Glycolysis The 10 reactions of glycolysis, summarized in Figure 20.16 "Glycolysis", can be divided into two phases. In the first 5 reactionsphase Iglucose is broken down into two molecules of glyceraldehyde 3-phosphate. In the last five reactionsphase IIeach glyceraldehyde 3-phosphate is converted into pyruvate, and ATP is generated. Notice that all the intermediates in glycolysis are phosphorylated and contain either six or three carbon atoms. Figure 20.16 Glycolysis.