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Name: Paula
Status: Other
Grade:  Other
Location: IL
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 inhibition.

Ron Baker, Ph.D.

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