Lipid bilayers form to remove the hydrophobic tails from the aqueous phase. The lipid tails face the interior of a biological membrane. Phospholipids, glycerolipids, and sphingolipids contain one or m...Lipid bilayers form to remove the hydrophobic tails from the aqueous phase. The lipid tails face the interior of a biological membrane. Phospholipids, glycerolipids, and sphingolipids contain one or more fatty acid chains as hydrophobic tails. The hydrophobic tail makes up most of the structure of sterols, excluding the hydroxl group. The shape and size of the lipid tail contribute significantly to the physical properties of the membrane.