Agar-Agar is gelatinous heteropolysaccharide produced in the cell wall of marine red algae such as species of Gelidium, Gracilaria, Gigartina, etc.
It is a mixture of sulphated heterpolysaccharides made up of D-galactose and L-galactose derivatives ether-linked between C3 and C6.
Agarose is the agar component with very few charged groups (sulfates, pyruvates). It has molecular weight in the range of 80,000-1,40,000. If agar and agarose are dissolved in hot water, they form solution which upon cooling sets to a gel. Agarose gels are used as inert support for the electrophoretic separation of nucleic acids. Agar is used to form a surface for the growth of bacterial and plant tissue cultures.