​  Chemically, agarose is a polysaccharide polymer, generally extracted from red algae or seaweed. Agarose is a linear polymer made up of repeating units of agarobiose, a disaccharide made up of D-galactose and 3,6-anhydro-L-galactopyranose. Agarose is one of the two principal components of agar, and is purified from agar by removing agar's other component, agaropectin.

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​  Agar is a complex mixture of polysaccharides extracted from the species of red algae known as agarophytes (Gelidium, Gracilaria, Pterocladia, Acanthopeltis and Ahnfeltia species). Bacteriological Agar is derived from red algae of the genus Gelidium and Pterocladia because Gracilaria and Gelidiella produce agars with gelling temperatures above 41°C.

​  Agar can be divided into two principal components;

1. Agarose a virtually neutral polymer, (1-4) linked 3,6-anhydro-L-galactose alternating with (1-3) linked ß-D- galactose

2. Agaropectin, a charged polymer, having the same repeating unit as Agarose but with some of the 3,6-anhydro-L-galactose residues replaced with Lgalactose sulphate residues, together with partial replacement of the Dgalactoseresidues with pyruvic acid acetal 4,6-0-(1-carboxyethylidene)-Dgalactose.

​  Agarose is the component responsible for the high-strength gelling properties of agar and the agaropectin provides the viscous properties.

​  There are several methods of producing highly purified agarose, many rely on the purification of Agar-Agar by removing the agaropectin from the agar. All such agars must be free from toxicity to micro-organisms and free from impurities such as non-agar gums, nitrogenous compounds, insoluble salts, free sugar compounds, dead micro-organisms and live thermophilic organisms. There are a limited number of highly specialized facilities that produce highly purified, high quality agarose under rigid physical-chemical, and bacteriological controls.