The Red Blood Cells

FUNCTION

• To absorb and transport oxygen from the lungs to body tissues

ADAPTATION TO FUNCTION

• Contain a red pigment called haemoglobin which is a protein molecule containing iron. In the lungs, the oxygen diffuses with the haemoglobin to form oxyhaemoglobin which is bright red. When it reaches a tissue, which needs oxygen, the oxyhaemoglobin gives up the oxygen to form haemoglobin again. Therefore haemoglobin enables the red blood cell to transport oxygen from the lungs to the body tissues.
• Red blood cells do not contain nuclei. Absence of the nucleus results in the red blood cell being circular and biconcave disc in shape. This increases the surface area to volume ratio so that oxygen can diffuse into or out of the whole cell at a faster rate. Therefore the rate of absorption and release of oxygen is faster.
• Red blood cells are extremely small and large in numbers and so have a very large total surface area for oxygen absorption making it a very efficient process.
• Red blood cells are flexible. they can become bell-shaped and so can pass along very narrow capillaries. This also decreases the rate of blood flow through the capillaries thus providing more time and increasing the efficiency for gaseous exchange.