In the fluid mosaic model of the cell membrane, mosaic refers to the cell membrane which is a collection of different proteins that are embedded within a phospholipid bilayer. The phospholipid bilayer is amphipathic which means the lipid bilayer has a hydrophobic region as well as a hydrophilic region.
Integral proteins are found in the hydrophobic interior region of the lipid bilayer and their hydrophilic regions are in contact with the surrounding watery environment. These proteins may contain a hydrophilic channel that works like a tunnel, allowing substances that are hydrophilic to pass through the membrane which is a key component of cell transport.
Proteins known as peripheral proteins are attached to the surface of the plasma membrane. Those attached on the cytoplasm side of the cell can attach to the cytoskeleton inside, and those attached to the extracellular side attach to fibers outside the cell--both of these proteins add support to the cell.
Some of the membrane proteins drift within the phospholipid bilayer while others are anchored. Membrane proteins perform vital functions including-- enzymatic activity, cell to cell attachment, transport of solutes across the membrane, and signal transduction-- a process whereby chemical messages are relayed into the cell using protein receptors on the membrane which allow hormones to have an effect on the cell. The cell membrane would be unable to perform its vital functions without the highly specialized proteins it contains.