FLUID MOSAIC MODEL 
Many models have been proposed to explain the molecular structure of plasma membrane. Fluid Mosaic Model was proposed by Singer and Nicolson in 1972 for the structure of plasma membrane which was universally accepted. According to this model the cell membrane has quasifluid structure. All cellular membranes line closed compartments and have a cytosolic and an exoplasmic face. Membranes are formed of lipids and proteins. According to this model the membrane is viewed as a two dimensional mosaic of phospholipids and protein molecules.
The phopholipid molecules form a continuous bilayer. The protein molecules are arranged as extrinsic proteins on the surface of lipid bilayer and as intrinsic proteins that penetrate the lipid bilayer either wholly or partially. The lipid bilayer is formed of a double layer of phopholipid molecules.  Each phospholid molecule has head and tail. Tails are Hydrophobic (water attracting) and heads are hydrophilic (water attracting). Lipid molecule is amphipathic. The arrangement of phospholipids forms a water resistant barrier. So that only lipid soluble substances can pass through readily but not water soluble substances. The phopholipid bilayer forms the basic structure of all biomembranes which also contains proteins, glycoproteins, cholesterol and other steroids and glycolipids. The presence of specific sets of membrane proteins permits each type of membrane to carry out distinctive functions.           
Peripheral proteins or extrinsic proteins are present on the inner and outer surfaces which are called as external proteins. These are superficially attached to either face of lipid bimolecular membrane and are easily removable by physical methods. It also has glycoproteins which are made up of carbohydrates, proteins, lipids, and fats.
Plasmalemma contains integral proteins or intrinsic proteins are the proteins that penetrate the lipid partially or wholly and are tightly held by strong bonds. In order to remove them the whole membrane has to be disrupted. The integral proteins occur in various forms and perform many functions.FLUID MOSAIC MODEL 
Many models have been proposed to explain the molecular structure of plasma membrane. Fluid Mosaic Model was proposed by Singer and Nicolson in 1972 for the structure of plasma membrane which was universally accepted. According to this model the cell membrane has quasifluid structure. All cellular membranes line closed compartments and have a cytosolic and an exoplasmic face. Membranes are formed of lipids and proteins. According to this model the membrane is viewed as a two dimensional mosaic of phospholipids and protein molecules.
The phopholipid molecules form a continuous bilayer. The protein molecules are arranged as extrinsic proteins on the surface of lipid bilayer and as intrinsic proteins that penetrate the lipid bilayer either wholly or partially. The lipid bilayer is formed of a double layer of phopholipid molecules.  Each phospholid molecule has head and tail. Tails are Hydrophobic (water attracting) and heads are hydrophilic (water attracting). Lipid molecule is amphipathic. The arrangement of phospholipids forms a water resistant barrier. So that only lipid soluble substances can pass through readily but not water soluble substances. The phopholipid bilayer forms the basic structure of all biomembranes which also contains proteins, glycoproteins, cholesterol and other steroids and glycolipids. The presence of specific sets of membrane proteins permits each type of membrane to carry out distinctive functions.           
Peripheral proteins or extrinsic proteins are present on the inner and outer surfaces which are called as external proteins. These are superficially attached to either face of lipid bimolecular membrane and are easily removable by physical methods. It also has glycoproteins which are made up of carbohydrates, proteins, lipids, and fats.
Plasmalemma contains integral proteins or intrinsic proteins are the proteins that penetrate the lipid partially or wholly and are tightly held by strong bonds. In order to remove them the whole membrane has to be disrupted. The integral proteins occur in various forms and perform many functions.

Fluid Mosaic Model for cell membrane was given by S.J.Singer and G.L.Nicholson in 1972. It says that the cell membrane is a phosholipid bilayer which had fluid like nature. in the bilayer of phospholipid, the hydrophobic part of the phospholipid molecules forms inner part of the membrane and it’s hydrophilic part forms the outer surface of the membrane. 

In the lipid bilayer, proteins are found.These proteins can be intrinsic i.e totally embedded in the lipid bilayer or can be extrinsic which are found on the surface of the membrane and can be extracted.

 

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