There are several ways that membrane proteins can associate with the cell membrane. Membrane proteins that extend through the lipid bilayer are called proteins and have regions that are exposed to the interior of the bilayer. On the other hand, membrane-associated proteins do not span the bilayer and instead associate with the membrane through an α helix that is . Other proteins are attached to lipid molecules that are inserted in the membrane. membrane proteins are linked to the membrane through noncovalent interactions with other membrane-bound proteins.