Bohr effect

The Bohr effect is a physiological phenomenon first described in 1904 by the Danish physiologist Christian Bohr, stating that haemoglobin's oxygen binding affinity (see Oxygen–haemoglobin dissociation curve) is inversely related both to acidity and to the concentration of carbon dioxide. Since carbon dioxide reacts with water to form carbonic acid, an increase in CO₂ results in a decrease in blood pH, resulting in hemoglobin proteins releasing their load of oxygen. Conversely, a decrease in carbon dioxide provokes an increase in pH, which results in haemoglobin picking up more oxygen.

In the early 1900s, Christian Bohr was a professor at the University of Copenhagen in Denmark, already well known for his work in the field of respiratory physiology. He had spent the last two decades studying the solubility of oxygen, carbon dioxide, and other gases in various liquids, and had conducted extensive research on haemoglobin and its affinity for oxygen. In 1903, he began working closely with Karl Hasselbalch and August Krogh, two of his associates at the university, in an attempt to experimentally replicate the work of Gustav von Hüfner, using whole blood instead of haemoglobin solution. Hüfner had suggested that the oxygen-haemoglobin binding curve was hyperbolic in shape, but after extensive experimentation, the Copenhagen group determined that the curve was in fact sigmoidal. Furthermore, in the process of plotting out numerous dissociation curves, it soon became apparent that high partial pressures of carbon dioxide caused the curves to shift to the right. Further experimentation while varying the CO₂ concentration quickly provided conclusive evidence, confirming the existence of what would soon become known as the Bohr effect.

There is some debate over whether Bohr was actually the first to discover the relationship between CO₂ and oxygen affinity, or whether the Russian physiologist Bronislav Verigo beat him to it, allegedly discovering the effect in 1898, six years before Bohr. While this has never been proven, Verigo did in fact publish a paper on the haemoglobin-CO₂ relationship in 1892. However, his proposed model was flawed, and Bohr harshly criticized it in his own publications.

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