Charged species transport discrimination

In the transport across a phospholipid bilayer by passive diffusion, the permeability of the neutral form of a molecule is 10X times greater than that of the charged form. For the epithelium, the discrimination factor is 105. The basement membrane (Fig. 2.5) allows passage of uncharged molecules more readily than charged species by a factor of 10 [76]. 

Porous membrane - Membrane made of porous material. When it separates liquid phases its performance depends on the size of the pores and chemical properties of the material. If pore size is much larger than the molecular dimensions, the membrane exerts no influence on transport of individual components of separated liquids and only prevents mixing by convection. For smaller pores it selectively controls transport of species between the phases discriminating them by the size and/or charge. See also - membrane system, - membrane electrode. 

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