Glucose is phosphorylated using ATP to form glucose-6- phosphate. This keeps the glucose in the cell as it cannot exit through glucose transporters and commits the glucose molecule to glycolysis. Phosphorylation also makes the glucose more reactive.Glucose-6-phosphate is isomerised to fructose phosphate. Another phosphate group is added from ATP and fructose-1,6-bisphosphate is formed. This breaks down into 2 triose phosphate molecules. The triose phosphate is converted into 2 pyruvate molecules.In the process of forming each pyruvate molecule, 2ATP are formed from the phosphate group of GALP, an inorganic phosphate from the cytoplasm and 2ADP molecules. NAD is reduced with the hydrogen from GALP.The formation of ATP in this way is called substrate level phosphorylation. In glycolysis 2ATP molecules are used and 4 ATP molecules are produced.