Describe in brief the fluid mosaic …

Singer and Nicolson proposed the fluid mosaic model of plasma membrane. 
The plasma membrane is composed of a lipid bilayer.
The lipid molecules are arranged in such a way that their polar head are towards the outer side and the hydrophobic tails are on the inner side.
This arrangement of lipid molecules ensures that the non-polar tail of hydrocarbons does not come in contact with the aquatic environment present.
The proteins are of two types. Integral proteins which are either partially or totally embedded in the lipid bilayer and peripheral proteins which are present on the surface of the membrane.
The quasi fluid nature of lipid enables the lateral movements of proteins within the lipid bilayer.
The fluid nature of the membrane enables functions such as cell growth, secretion, endocytosis, cell division and formation of the intercellular junction.