The Function of Normal Human Hemoglobin

Hemoglobin binds oxygen in the lungs and then gives it up for metabolism in the tissues. For hemoglobin to do that, it must also keep its hold on oxygen molecules in a Goldilocks zone of “not too tight, not too loose.” A number of factors tweak that zone including carbon dioxide and acidity, 2,3-biphosphoglycerate, and temperature. Hemoglobin’s tetrameric structure permits the subunits to cooperate in the binding and release of oxygen, displayed graphically as the S-shaped “hemoglobin-oxygen dissociation curve”, central to hemoglobin function. The dominant hemoglobin during fetal life is able to pull oxygen off the mother’s adult hemoglobin. Hemoglobin also performs yet another essential task, giving the smallest blood vessels a signal to dilate and optimize blood flow. Thus, hemoglobin not only carries oxygen, but also helps expedite its delivery.