Erythrocyte can not derive energy from fat. Main energy resource is glucose. Why?
Glucose is the main representative of carbohydrates (monosaccharides). The main energy substrate of the body. In the process of the collapse of one glucose molecule synthesized 38 molecules of ATP. The main hormone responsible for the disposal of excess glucose is insulin. All the energy released in the process of splitting glucose to pyruvate is 146 kJ / mol, the synthesis of two molecules of ATP consumed 61 kJ / mol, the remaining 85 kJ / mol energy is converted into heat . When complete oxidation of glucose to carbon dioxide and water released 2840 kJ / mol, if we compare this value with an overall yield of other reactions of glycolysis (146 kJ / mol), it becomes clear that 95% of the energy of glucose remains a "prisoner" in molecules pyruvate. Although the reactions of glycolysis are universal for almost all organisms, the fate of its products - pyruvate and NADH - varies creatures and depend on circumstances. Glycolysis is almost universal to all cellular organisms through the catabolism of glucose. Perhaps he arose early in the development of life on Earth, even before oxygen accumulated in the atmosphere as a result of photosynthetic organisms.