In carbon monoxide
poisoning the CO replaces the \(\textsf{O}_{2}\) adsorbed on
hemoglobin (\(\text{Hb}\)) molecules in the blood. To show the effect,
consider a model for which each adsorption site on a heme may be
vacant or may be occupied either with energy \(\varepsilon_A\) by one
molecule \(\textsf{O}_{2}\) or with energy \(\varepsilon_B\) by one
molecule CO. Let \(N\) fixed heme sites be in equilibrium with
\(\textsf{O}_{2}\) and CO in the gas phases at concentrations such
that the activities are \(\lambda(\text{O}_2) = 1\times 10^{-5}\) and
\(\lambda(\text{CO}) = 1\times 10^{-7}\), all at body temperature
\(37^\circ\text{C}\). Neglect any spin multiplicity factors.
First consider the system in the absence of CO. Evaluate
\(\varepsilon_A\) such that 90 percent of the \(\text{Hb}\) sites
are occupied by \(\textsf{O}_{2}\). Express the answer in eV per
\(\textsf{O}_{2}\).
Now admit the CO under the specified conditions. Fine
\(\varepsilon_B\) such that only 10% of the Hb sites are occupied
by \(\textsf{O}_{2}\).