Description
Hemoglobin is found in the erythrocytes of all vertebrates. It is a conjugated protein with the prosthetic group heme which contains iron. The heme group is involved with the transport of oxygen from the lungs to tissues, while the globin portion of hemoglobin plays a major role in transporting carbon dioxide from the tissues to the lungs. The iron in heme is in the ferrous state. In oxyhemoglobin, it is apparently still in the ferrous state, but the oxygen is loosely bound to it.
The structure of the hemoglobin molecule has been extensively studied. Most of the mammalian hemoglobins are composed of four subunits, consisting of four peptide chains to each of which is attached a heme group. But, among the mammalian hemoglobins, there are structural differences in terms of the amino acid residues and their sequences in the polypeptide chains. The molecular weight of hemoglobin is about 66,000 and the iron content is about 0.34%. The principal applications for hemoglobin are as a substrate for proteases, in anemia diagnosis and as a marker during molecular weight determination.