Breakdown Of The Red Blood Cell

As a red cell ages, there will be a decrease in many of its enzymes, a decrease in ATP, and the cell will tend to become smaller and slightly more dense. Destruction of the red blood cell most commonly occurs in the bone marrow, through phagocytosis by the reticuloendothelial cells. As soon as this occurs, there is breakdown of the hemoglobin. The iron is freed for reuse by new red cells, and the amino acids, from the globin, are returned to the amino acid pool. The protoporphyring ring is broken at one of the methene bridges and biliverdin is formed. The biliverdin is reduced to bilirubin, which is carried by the plasma albumin to the liver for eventual excretion. If hemoglobin is released directly into the blood, it becomes attached to haptoglobin (a globulin), taken to the reticuloendothelial cell, and processed in the normal way. Free hemoglobin in the blood may be oxidized to methemoglobin. The heme groups will then combine with hemopexin, leave the circulation, and be catabolized. If there is an excess of heme groups, they will combine with albumin to form methemalbumin until hemopexin becomes available.