Hemoglobin (HB)

Hemoglobin is the iron-containing oxygen-transport metalloprotein in the red blood cells of vertebrates, and the tissues of some invertebrates.In mammals, the protein makes up about 97% of the red blood cell’s dry content, and around 35% of the total content. Hemoglobin transports oxygen from the lungs or gills to the rest of the body where it releases the oxygen for cell use. It also has a variety of other roles of gas transport and effect-modulation which vary from species to species, and are quite diverse in some invertebrates. Hemoglobin has an oxygen binding capacity of between 1.36 and 1.37 ml O₂ per gram of hemoglobin, which increases the total blood oxygen capacity seventyfold.Hemoglobin is found in nonerythroid cells including the A9 dopaminergic neurons in the substantia nigra, macrophages, alveolar cells, and mesangial cells in the kidney.