Why red blood cells does not contain nucleus?
One of the often recited rules in Biology is that all living things possess a nucleus. This is generally true but the red blood cell is a significant exception to this rule. It develops from progenitor cells with nuclei but as red blood cells mature, they lose their nucleus completely. This is all part of the red blood cell’s adaptations for its function of carrying oxygen around the body. Each cell is packed with a protein called haemoglobin, which attracts oxygen very strongly when blood flows through the lungs. The oxygen passes from the air in the alveoli and into the blood through the alveoli and capillary wall. Because the red blood cell has no nucleus (which would be a large spherical structure in the middle of the cell) it can use all of its volume for haemoglobin, so can carry as much oxygen as possible. Its other adaptation to its function is that it has a biconcave shape – this enables it to have a large surface area for picking up oxygen in the first place.
