Which substances cannot diffuse through the lipid bilayer?

Is the lipid bilayer permeable to most water-soluble substances?

• Answer:

  The lipid bilayer is impermeable to most water-soluble substances. The bilayer, most of which is a phospholipid bilayer, is permeable only to small, non-polar substances. In nature, the most common compounds to pass through the bilayer are carbon dioxide and oxygen. Scientists differ over how much water passes in and out of cells through the bilayer; some passes through special transport proteins called aquaporins.