CO and Oxygen Exchange
Country: United States
Date: November 2008
Hello, I was told that if you administer 100% O2 to a
person with carbon monoxide poisoning, the O2 will replace the CO
molecules on the hemoglobin. I know that hemoglobin has a much
greater affinity for CO than for O2. What would cause the hemoglobin
to release to CO molecule for a O2 molecule?
When oxygen or carbon monoxide binds to hemoglobin, they aren't locked there
forever. They eventually will unbind. Random fluctuations in the molecules
(thermal energy) eventually will cause the molecules to unbind. "Greater
affinity" means that the fit is tighter, but it's still not absolutely
permanent. If you surround the hemoglobin with oxygen molecules, when the CO
eventually unbinds, it's more likely that an oxygen will take its space
rather than a CO molecule.
Hope this helps,
When 2 molecules bind together non-covalently, they are not bonded together
permanently. Because of thermal motion, they establish an equilibrium between
bonded and separated. This applies to CO and Hb, so the more Oxygen there is
around, every time a CO molecule dissociates from Hb, the more likely it is
that it will be replaced by an Oxygen molecule. It's known as competitive
Ron Baker, Ph.D.
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Update: June 2012