Describe the fluid mosaic model of plasma membrane.

Fluid-Mosaic model is the most recent model of a biomembrane proposed by Singer and Nicolson in 1972. According to this model, the membrane does not have a uniform disposition of lipids and proteins but is instead a mosaic of the two. Further, the membrane is not solid but is quasifluid. The quasifluid nature of the membrane is shown by their properties of quick repair, dynamic nature, ability to fuse,expand and contract, grow during cell growth and cell division, secretion, endocytosis and formulation of intercellular junctions.
Fluid-Mosaic model postulates that the lipid molecules are present in a viscous bilayer as in lamellar model. Protein molecules occur at places both inside and on the outer side of lipid bilayer- protein icebergs in a sea of lipids. The internal proteins are called intrinsic or integral proteins while the external ones are known as extrinsic or peripheral proteins.