Mechanistic formalism for membrane transport generated by osmotic and mechanical pressure.

Since the physical interpretation of practical Kedem-Katchalsky (KK) equations is not clear, we consider an alternative, mechanistic approach to membrane transport generated by osmotic and hydraulic pressure. We study a porous membrane with randomly distributed pore sizes (radii). We postulate that reflection coefficient (sigma p) of a single pore may equal 1 or 0. From this postulate we derive new (mechanistic) transport equations. Their advantage is in clear physical interpretation and since we show they are equivalent to the KK equations, the interpretation of the latter became clearer as well. Henceforth the equations allow clearer and more detailed interpretation of results concerning membrane mass transport. This is especially important from the point of view of biophysical studies on permeation processes across biological membranes, cell membranes including.