Re: Do red blood cells breath or metabolize? Are they even 'alive'?

Red cells are certainly alive, they have an intact cell membrane and contain numerous enzymes and other proteins which carry out a variety of metabolic functions. They use sugars like most living things to produce energy. In fact their survival is dependent on the continuous use of sugars such as glucose for energy which is used to to to operate a pumping mechanism in the red cell membrane to maintain the normal gradients (differences in concentrations) of ions such as sodium. Energy is also required to convert methemoglobin to oxyhemoglobin and to prevent the oxidation of other constituents of the red cell.

Since the erythrocyte lacks a nucleus, the amount of oxygen required by the cell for its own metabolism is very low, and most of the oxygen carried by the hemoglobin can be freed into the tissues.

Red blood cells are produced in the bone marrow. The precursor cell is call an erythroblast. It has a nucleus but does not produce hemoglobin. As the cell matures hemoglobin appears and the nucleus and mitochondria becomes progressively smaller. After several days the nucleus disappears completely and the cells enter the bloodstream. Mature red blood cells have a life span of about 120 days. Since they can't produce proteins they are unable to repair any damage that might occur and eventually the metabolic activities necessary for survival are impaired. Such damaged red blood cells are taken up by phagocytic cells which destroy the damaged red blood cells.