Final answer:
The source of energy in erythrocytes is glycolysis, the anaerobic pathway of breaking down glucose to produce ATP, since these cells lack mitochondria and must utilize a primitive metabolic pathway to meet their energy requirements.
Step-by-step explanation:
The source of energy in erythrocytes, or red blood cells, comes from glycolysis, which is the process of breaking down glucose to produce ATP. Erythrocytes are unique in that they lack a nucleus and mitochondria; therefore, they do not possess the cellular machinery for aerobic respiration and rely solely on anaerobic respiration. The absence of mitochondria ensures that erythrocytes do not consume any of the oxygen they are designed to transport. Instead, they use a primitive but effective metabolic pathway to meet their energy needs. However, in conditions such as pyruvate kinase deficiency, the final step of glycolysis is disrupted, leading to an energy production deficit, which can cause damage to the erythrocyte membrane, resulting in premature cell destruction.