Cell membrane has many protein like
integral, extrinsic having function of cell signalling, cell to
cell recognition, transport etc.
So there is need to confine
proteins to specific domain dor there catalytic activity and
functioning.
Some domains like cytoplasmic and
extracellular domain are responsible for the signal amplification
and signal receiving respectively.
specific domain of each protein may
be buried inside lipid bilayer to make proteins diffusible by there
hydrophobic amino acid domains and some polar domains are present
in protein on membrane proteins.