Because of the lipoid nature of the cell membrane, it is highly permeable to lipid soluble substances a Because biologic cells are also permeated by water and lipid-insoluble substances, it is thought that the membrane also contains water-filled pores or channels that permit the passage of these types of substances◼ Because of the lipoid nature of the cell membrane, it is highly permeable to lipid soluble substances. ◼ Because biologic cells are also permeated by water and lipid-insoluble substances, it is thought that the membrane also contains water-filled pores or channels that permit the passage of these types of substances