Molecular structure of the red blood substance (hemoglobin) which is found in red blood cells (erythrocytes) and is named after its name (because of hem). Adult HbA1 consists of four subunits (polypeptide chain as a tetramer): Two alpha-protein-chains and two beta-protein chains which are made of a ferritic porphyrin ring, hem, as a prosthetic group and the globulin. The molecular arrangement of the chains adjusts (conformation change) which is necessary for oxygen to bind and be released. Transport of gas is the main task of erythrocytes.
