The cell membrane is a semi-permeable barrier between the

cell interior and its surroundings. One of the mechanisms for

transmembrane transport involves the presence of pores in the lipid

bilayer, through which a substantial flow of material can take place.

For example, pores were observed in red blood cell ghosts (Lew

et al., 1982; Lieber and Steck, 1982a,b), where the pore size depends

on the ionic strength of the surrounding fluid (Lieber and Steck,