 It is a protective sheath of cell
 Exchanges material
 Facilitate interaction between cells

 Bilipid layer
 Thickness 7-10 nm
 Lipids 42%
 Proteins 55%
 Carbohydrate 3%

 Consists of double layered phospholipid
 Allows the flexibility of the membrane without
disturbing structural integrity
 Diffusion within the membrane is called
translational diffusion

 Effect of TEMPERATURE
 Role of CHOLESTEROL
At temp , cholesterol fluidity
At temp, cholesterol fluidity

 Creates permeability barrier
 Permeability depends on solubility
 Lipid soluble substance can pass through
membrane
Eg: oxygen & alcohol
 Water soluble substance cannot pass easily
Eg: glucose & urea

Membrane Proteins
o Integral
o Peripheral
 Functions of proteins
1. Serves as channel proteins
2. Act as carriers , serves as pumps
3. Antigenic , serves as receptor
4. Cell adhesion molecules

Membrane Carbohydrates
 Glycocalyx
Functions
• Serves as protective coat
• Selectins (permit temporary cell-to-cell adhesion)
• Integrins (permit strong cell-to-cell adhesion)

Special type
integral proteins
 Glycophorins
 Band-3 protein
Peripheral proteins
 Spectin
 ankyrin