What Keeps Proteins Within the Lipid Bilayer?

Proteins are kept within the lipid bilayer of a cell by a number of different means depending on their type. Integral proteins extend through the lipid bilayer to make contact with the interior of the cell, where their hydrophobic regions are protected from water. Lipid-bound proteins are held entirely within the lipid bilayer by a glycosylphosphatidylinositol anchor.