[The higher structure and physiological significance of hemoglobin]

The major function of hemoglobin, which is known as a highly advanced allosteric protein, is the transportation of oxygen and carbon dioxide between the lung and the tissues. Hemoglobin not only has the capability of binding a large quantity of oxygen but also the property of releasing oxygen in tissues where the pressure of oxygen is reduced with increase in the pressure of carbon dioxide. Thus, the blood can efficiently carry oxygen from the lung to the tissues. This physiological phenomenon is related strongly to the interaction between the higher structure of hemoglobin and various kinds of ions, e.g., H+, HCO3-, and 2,3-diphosphoglycerate.