Facilitated Diffusion of Oxygen through Hæmerythrin Solutions

Abstract

HÆMOGLOBIN present in water solution facilitates the steady-state diffusion of oxygen through that solution^1,2; the total oxygen flux is greater than the flux through an equivalent protein solution, for example, a solution of methæmoglobin. The hæmoglobin-mediated oxygen flux may be considered to be additive to the simple diffusion flux of oxygen. Fig. 1, which although obtained with the protein hæmerythrin is entirely typical of results obtained with hæmoglobin, reveals that the flux mediated by an oxygen-binding protein is constant in amount for a particular protein concentration and independent of the oxygen partial pressure difference across the solution at oxygen partial pressures sufficient to saturate largely the carrier. This property has the interesting consequence that at the low oxygen partial pressure presumably existing in tissue the hæmoglobin mediated flux would be expected to make up the largest part of the total oxygen flux. Quite possibly the facilitation of oxygen diffusion in the interior of muscle cells is a major function of myoglobin.