Hemoglobin (Hb)

Hemoglobin is the primary oxygen-carrying metalloprotein in the red blood cells (erythrocytes) of vertebrates, responsible for binding oxygen in the lungs and releasing it in tissues throughout the body. Each hemoglobin molecule consists of four globin subunits, each containing an iron-bound heme group capable of reversibly binding one oxygen molecule, allowing each tetrameric hemoglobin to carry four oxygen molecules. The process is tightly regulated by allosteric interactions influenced by oxygen tension, carbon dioxide, hydrogen ion concentration, and temperature. Besides oxygen transport, hemoglobin also facilitates carbon dioxide and nitric oxide transport, contributing to the regulation of blood flow and vascular tone. Abnormalities in hemoglobin structure or erythrocyte function cause diseases such as anemia, sickle cell disease, and thalassemia, with clinical consequences related to impaired oxygen delivery and vascular complications[1][2][3][4][5][6][7][8].

Other names

Erythrocyte oxygen transporterRed blood cell oxygen transportHemoglobin proteinOxyhemoglobin (for the oxygen-bound form)

Reversible binding of oxygen to the iron in the heme component of hemoglobin enables transport from lungs to tissues[5][3][4][7] Modulation of oxygen release by changes in pH, carbon dioxide, and temperature (Bohr effect)[5][3][7] Facilitation of carbon dioxide transport as carbamino-hemoglobin and via bicarbonate conversion Participation in nitric oxide metabolism, affecting vascular tone[1][2][6]