n.
a substance contained within the red blood cells (erythrocyte) and responsible for their colour, composed of the pigment haem (an iron-containing porphyrin) linked to the protein globin. Haemoglobin has the unique property of combining reversibly with oxygen and is the medium by which oxygen is transported within the body. It takes up oxygen as blood passes through the lungs and releases it as blood passes through the tissues. Blood normally contains 12-18 g/dl of haemoglobin. See also myohaemoglobin, oxyhaemoglobin.
Medical dictionary. 2011.