Involved in oxygen transport from gills to the various peripheral tissues. Hb 2 is a heterotetramer of two alpha-2 and two beta-1 chains. Hb 3 is a heterotetramer of two alpha-2 and two beta-2 chains. Red blood cells. Hb 3 displays a Bohr effect, which is enhanced by organophosphates, and a Root effect, which is enhanced by ATP. Belongs to the globin family.