Plasma Membrane :

Plasma Membrane is the outermost boundary of the animal cell. It is also known as cell membrane or plasmalemma. 

Composition:

• Lipids 20-40%
• Proteins 60-80%
• Carbohydrates 1% 

Structure:

It contains a lipid bilayer made of phospholipids in which the proteins are embedded. These proteins are not continuous rather embedded in a mosaic manner that is why the structure most widely accepted is known as the fluid mosaic model. 

The unit membrane model suggests that there is a continuous protein layer with phospholipids sandwiched in between. however this structure is not accepted.

Lipids: 

Lipids in plasma membrane are of 2 types :

Phospholipids which maintain the fluidity of the membrane and sterols which provide stability to the membrane. 

Proteins:

Proteins may be integral proteins or non integral. They maybe transmembrane proteins or extrinsic and intrinsic proteins which are only present on the surface of the membrane. 

Carbohydrates:

Carbohydrates are majorly conjugated forms of oligosaccharides with lipids or proteins called the glycolipids and the glycoproteins. They are collectively called the glycocalyx which helps in the cell recognition process. 

Functions Of Cell Membrane :

• It is a selectively permeable membrane. Allows only certain substances to pass through. So it is involved in the regulation.
• It is involved in transport of materials in and out of membrane through the active and passive transport.
• It is involved in movement of water through osmosis.
• It is involved in endocytosis and exocytosis 
• It is involved in nerve impulse conduction