Bohr effect The effect of pH on the dissociation of oxygen from haemoglobin, first discovered by the Danish physiologist Christian Bohr (1855–1911). An increase in carbon dioxide concentration makes the blood more acidic and decreases the efficiency of the uptake of oxygen by haemoglobin molecules. This shifts the oxygen dissociation curve to the right and increases the tendency of haemoglobin to release oxygen (see haemoglobinic acid). Thus in actively respiring tissues, where the concentration of carbon dioxide in the blood is high, haemoglobin readily releases its oxygen, while in the lungs, where blood carbon dioxide is low (due to its continual diffusion into the alveoli), haemoglobin readily binds oxygen.

Bohr effect A decrease in the affinity of haemoglobin for oxygen and a shift of the oxygen-dissociation curve to the right, brought about either by a decrease in pH or by an increase in the partial pressure of carbon dioxide, such that a high concentration of carbon dioxide causes more oxygen to be given up at any given oxygen pressure (e.g. in the tissues). It is an important mechanism in the release of oxygen by haemoglobin in the blood in respiratory tissues, where the partial pressures of carbon dioxide are high.