Гемоглобин мен оттегінің байланысы: Халдейн эффектісі

Property of hemoglobin and oxygenation
The Haldane effect is a property of hemoglobin first described by John Scott Haldane, within which oxygenation of blood in the lungs displaces carbon dioxide from hemoglobin, increasing the removal of carbon dioxide. Consequently, oxygenated blood has a reduced affinity for carbon dioxide. Thus, the Haldane effect describes the ability of hemoglobin to carry increased amounts of carbon dioxide (CO2) in the deoxygenated state as opposed to the oxygenated state. Vice versa, it is true that a high concentration of CO2 facilitates dissociation of oxyhemoglobin, though this is the result of two distinct processes (Bohr effect and Margaria Green effect) and should be distinguished from Haldane effect.

Carbon dioxide travels through the blood in three different ways. One of these ways is by binding to amino groups, creating carbamino compounds. Amino groups are available for binding at the N terminals and at side chains of arginine and lysine residues in hemoglobin. When carbon dioxide binds to these residues carbaminohemoglobin is formed. This amount of carbaminohemoglobin formed is inversely proportional to the amount of oxygen attached to hemoglobin. Thus, at lower oxygen saturation, more carbaminohemoglobin is formed. These dynamics explain the relative difference in hemoglobin's affinity for carbon dioxide depending on oxygen levels known as the Haldane effect.

Histidine residues in hemoglobin can accept protons and act as buffers. Deoxygenated hemoglobin is a better proton acceptor than the oxygenated form.

In patients with lung disease, lungs may not be able to increase alveolar ventilation in the face of increased amounts of dissolved CO2. This partially explains the observation that some patients with emphysema might have an increase in PaCO2 (partial pressure of arterial dissolved carbon dioxide) following administration of supplemental oxygen even if content of CO2 stays equal.