Biopolymers, Such As Chitin, Are Natural Polymers Produced By Organisms

Chitin

Chitin is a long-chain polymer of N-acetylglucosamine, a glucose amide derivative.  Polysaccharide is the second most abundant polysaccharide in nature (after cellulose), with an estimated 1 billion tonnes produced in the biosphere each year. It is a primary component of fungi cell walls, arthropod exoskeletons such as crustaceans and insects, and molluscan radulae, cephalopod beaks, and gladii. At least some fish and lissamphibians synthesise it as well. Polysaccharide has a similar structure to cellulose, forming crystalline nanofibrils or whiskers. It functions similarly to the protein keratin. Polysaccharide has been found to be useful in a variety of medicinal, industrial, and biotechnological applications.

Polysaccharide is translucent, pliable, resilient, and quite tough in its natural, unaltered state. However, in most arthropods, it is frequently modified, appearing primarily as a component of composite materials, such as sclerotin, a tanned proteinaceous matrix that forms much of the exoskeleton of insects. Chitin produces a much stronger composite when combined with calcium carbonate, as in the shells of crustaceans and mollusks. This composite material is tougher and less brittle than pure calcium carbonate and much harder and stiffer than pure polysaccharide. Another distinction between pure and composite forms can be seen by contrasting a caterpillar's flexible body wall (primarily polysaccharide) with a beetle's stiff, light elytron (containing a large proportion of sclerotin).

Polysaccharide is a nitrogen-containing modified polysaccharide synthesised from units of N-acetyl-D-glucosamine (specifically, 2-(acetylamino)-2-deoxy-D-glucose). These units combine to form covalent -(14)-linkages (like the linkages between glucose units forming cellulose). As a result, Chitin Market can be defined as cellulose with one hydroxyl group replaced by an acetyl amine group on each monomer. This allows for increased hydrogen bonding between adjacent polymers, increasing the strength of the chitin-polymer matrix. Humans and other mammals have chitinase and chitinase-like proteins that can degrade polysaccharide, as well as immune receptors that can recognise polysaccharide and its degradation products and initiate an immune response.