Question

The alveolar epithelium, basement membrane and lung capillary endothelium are typically 1 µm thick. under resting conditions, hemoglobin binding with oxygen reaches a steady state of about 0.33 seconds. is oxygen diffusion across the alveolus a significant factor in the time required for the hemoglobin to oxygenate as it transverses the capillary?

Answer 1

The Hb or hemoglobin refers to a molecule of protein present in RBCs or erythrocytes comprising of four subunits; two beta and two alpha subunits. Each subunit envelopes a heme group in the center, which comprises iron and attaches one molecule of oxygen, permitting each molecule of hemoglobin to combine with four molecules of oxygen.

In the given case,

Diffusion time = L^2/D^ij = (10^-4 cm)^2/2*10^-5 cm^2/s = 0.0005 sec

With a diffusion time of 0.0005 sec, it can be seen that diffusion is much faster in comparison to the reaction time of 0.33 sec. Thus, diffusion does not interrupt the procedure of oxygenation.