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The Haldane effect is a property of hemoglobin first described by John Scott Haldane. Oxygenation of blood in the lungs displaces carbon dioxide from hemoglobin which increases the removal of carbon dioxide. This property is the Haldane effect. 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 CO 2 in the deoxygenated state as opposed to the oxygenated state.
A high concentration of CO 2 facilitates dissociation of oxyhemoglobin. Carbon dioxide can bind 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. This forms carbaminohemoglobin. Carbaminohemoglobin is the major contributor to the Haldane effect. Histidine residues in hemoglobin can accept and act as buffers. Deoxygenated hemoglobin is a better proton acceptor than the oxygenated form.
In red blood cells, the enzyme carbonic anhydrase catalyzes the conversion of dissolved carbon dioxide to carbonic acid , which rapidly dissociates to bicarbonate and a free proton :. By Le Chatelier's principle , anything that stabilizes the proton produced will cause the reaction to shift to the right, thus the enhanced affinity of deoxyhemoglobin for protons enhances synthesis of bicarbonate and accordingly increases capacity of deoxygenated blood for carbon dioxide.
The majority of carbon dioxide in the blood is in the form of bicarbonate. Only a very small amount is actually dissolved as carbon dioxide, and the remaining amount of carbon dioxide is bound to hemoglobin. In addition to enhancing removal of carbon dioxide from oxygen-consuming tissues, the Haldane effect promotes dissociation of carbon dioxide from hemoglobin in the presence of oxygen. In the oxygen-rich capillaries of the lung, this property causes the displacement of carbon dioxide to plasma as low-oxygen blood enters the alveolus and is vital for alveolar gas exchange.
However, this equation is confusing as it reflects primarily the Bohr effect. In patients with lung disease, lungs may not be able to increase alveolar ventilation in the face of increased amounts of dissolved CO 2. This partially explains the observation that some patients with emphysema might have an increase in P a CO 2 partial pressure of arterial dissolved carbon dioxide following administration of supplemental oxygen even if content of CO 2 stays equal.
From Wikipedia, the free encyclopedia. This section does not cite any sources. Please help improve this section by adding citations to reliable sources. Unsourced material may be challenged and removed. Nunn's Applied Respiratory Physiology 5th ed. Butterworth Heinemann. Scandinavian Journal of Clinical and Laboratory Investigation.
The Bohr effect is a physiological phenomenon first described in by the Danish physiologist Christian Bohr. Hemoglobin '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 CO 2 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 hemoglobin picking up more oxygen. In the early s, Christian Bohr was a professor at the University of Copenhagen in Denmark, already well known for his work in the field of respiratory physiology. 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. Another challenge to Bohr's discovery comes from within his lab.