Haldane effect

The Haldane effect describes the way in which CO2 is discharged via erythrocytes. The more oxygen-rich blood gives the charged oxygen to the tissue, the better it can absorb carbon dioxide. The Haldane effect was first described by John Scott Haldane.

In the interior of breathing oxygen is exchanged for carbon dioxide in the capillaries. The transport of oxygen to the tissues is largely adopted in vertebrates by the protein hemoglobin, which is present in high concentration in the erythrocytes.

If the oxyhemoglobin ( = with oxygen -laden hemoglobin) gives the charged oxygen to the tissues and becomes deoxyhemoglobin increases its affinity to H . H binds primarily to basic amino acid residues or the terminal group of the hemoglobin. This increases the pH in the erythrocytes.

CO2 with water can go under physiological conditions with the aid of carbonic anhydrase following reaction:

Carbon dioxide forms carbonic acid in the blood with water, which in turn dissociates to proton and bicarbonate ion.

By withdrawing the H balance massively on the side of the bicarbonate ( = bicarbonate ) is drawn. The gaseous uncharged CO2 can diffuse freely through the lipid membranes of the cells, the charged HCO3- but not. The HCO3- is from the erythrocytes over a antiporter in exchange for Cl - discharged (Hamburger shift).

Get the erythrocyte then back into the pulmonary alveoli, they take the bicarbonate again. The hemoglobin in the erythrocytes increases due to the high oxygen partial pressure O2, which, in turn, the affinity of hemoglobin for H decreases and H released. By now lowered pH, the equilibrium ( above formula! ) Shifts to the side of the gaseous CO2 that can diffuse freely through the membranes. The CO2 formation is enhanced, since CO2 is released via the pulmonary epithelium due to the partial pressure gradient to the outside air.