Gas transport of carbon dioxide |
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Carbon dioxide, released by cells, is mixed with the blood serum to make carbonic acid. Carbonic acid, being a relatively strong acid, dissociates into bicarbonate and a hydrogen ion. The carbon dioxide itself, however, can also participate in oxygen release.
The carbon dioxide molecule interacts with the last amino acid of the haemoglobin protein molecules to cause a structural change that causes the release of oxygen molecules that are bound to it. This phenomenon, known as the Bohr effect, is a highly adaptive feature of the body's blood-gas exchange mechanism. The blood that is pumped from the heart to the body tissues and organs (other than the lungs) is rich in oxygen. As oxygen rich blood arrives at the tissues it encounters an environment that is high in carbon dioxide and H+ ions that are products from the metabolic processes. Carbon dioxide attaches to the haemoglobin proteins and causes the release of oxygen where it is needed. H+ ions produced from the chemical reaction between carbon dioxide and water, as outlined in the video on the right. This causes oxygen to be released where it is needed most.
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It is important for oxygen to stay attached to the haemoglobin as it is travelling through the blood vessels on its way to the tissues. The blood pH, which is a measure of the concentration of H+ ions, remains relatively stable. This changes at the tissues where the H+ ion concentration increases thus stimulating the release of oxygen where it is needed.
What is carbonic anhydrase?
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