Fluid Mosaic Lipid:
Phospholipids form a bilayer in which the nonpolar regions of the lipid
molecules in each layer face the core of the bilayer and their polar head groups
face outward, interacting with the aqueous phase on either side. Proteins are
embedded in this bilayer sheet, held by hydrophobic interactions between the
membrane lipids and hydrophobic domains in the proteins. Some proteins
protrude from only one side of the membrane; others have domains exposed on
both sides. The orientation of proteins in the bilayer is asymmetric, giving the
membrane ‘sideness’: the protein domains exposed on one side of the bilayer are
different from those exposed on the other side, reflecting functional symmetry.
The membrane mosaic is fluid because most of the interactions among its
components are noncovalent, leaving individual lipid and protein molecules free
to move laterally in the plane of the membrane.
They are firmly associated with the lipid bilayer and are removable only by
agents that interfere with hydrophobic interactions, such as detergents, organic
solvents, or denaturants.
Its amino-terminal domain (bearing the carbohydrate chains) is on the outer
surface and is cleaved by trypsin. The carboxyl terminus protrud