Final answer:
Peripheral proteins are loosely associated with the surface of the lipid bilayer and can be attached to integral proteins or the polar head groups of phospholipids.
Step-by-step explanation:
Peripheral proteins are proteins that are loosely associated with the surface of the lipid bilayer. They can be attached to integral proteins or the polar head groups of phospholipids through non-covalent interactions. On the other hand, integral proteins span the hydrophobic interior of the lipid bilayer.