The main source of energy for mature erythrocytes is glycolysis. 1. There are no mitochondria in mature erythrocytes, so the aerobic oxidation of sugar, fatty acid oxidation and other energy-supplying pathways can not be carried out, and some reactions in the non-energy-supplying pathways such as gluconeogenesis and amino acid catabolism need to be carried out in the mitochondria, so the above energy-supplying and non-energy-supplying reactions can not be carried out in the erythrocytes. 2. Glycolysis is accomplished in the cytoplasm and does not require the presence of mitochondria, and the process of glycolysis can provide a small amount of energy for the erythrocytes. Furthermore, glycolysis transfers the released free energy to adenosine triphosphate. 3. Glycolysis is also a common pathway for the degradation of hexoses such as fructose, mannose, and galactose. Fructose and mannose can be converted to fructose-6-phosphate through the catalytic action of hexokinase, and fructose can also be converted to glyceraldehyde 3-phosphate through the action of a series of enzymes. Galactose can be converted to glucose 1-phosphate catalyzed by a number of enzymes.