ABSTRACT
The process of red blood cells (RBC) production is called erythropoiesis. RBCs start as immature cells in the red bone marrow and after about seven days of maturation they are released into the bloodstream. RBCs survive for about 120 days. Their cell membranes are exposed to a lot of wear and tear as they squeeze through blood capillaries. Without a nucleus and other organelles, RBCs cannot synthesise new components. Worn out RBCs are removed from the circulation and destroyed by fixed phagocytic macrophages in the spleen and the liver and the breakdown products are recycled. The haemoglobin molecule is a tetramer composed of four subunits. Each subunit consists of a polypeptide chain in association with a haem group. A haem group consists of a central charged iron atom held in a ring structure called a porphyrin.
