Facilitated diffusion of oxygen in the presence of hemoglobin

Abstract

The basic equations for the simultaneous diffusion and chemical reactions of oxygen and emoglobin in a film at steady state were solved assuming that the total oxygen flux was the sum of the ux by plain diffusion and that by diffusion of oxyhemoglobin. After collecting and scrutinizing the ertinent numerical data, particularly for the diffusion coefficients of oxygen and hemoglobin, numeri solutions were obtained by computer for a variety of conditions. It appeared that the gradients of xygen and oxyhemoglobin across the slab were notably different from those stipulated for the andition of chemical equilibrium. In particular we found that there must be a minute step in the oxygen gradient at the low pressure side with a slope equal to that at the high pressure side because f the boundary condition that the two surfaces must be impermeable for hemoglobin, and that the saturation is higher at the low pressure side and lower at the high pressure side than at chemical equilibrium. When assuming mean values from available data for the diffusion coefficients of oxygen and hemoglobin we arrived at excellent agreement between the computed fluxes and those obtained experimentally by other authors. It is concluded that the facilitation of oxygen diffusion in the presence of hemoglobin can be described quantitatively when the chemical reactions are taken into account.