The chitin molecule in 3-D

The Chitin molecule - rotatable in 3 dimensions

This model - effectively a section of a chitin microfibril - shows a strip of eight N-acetylglucosamine units joined by alternating β (beta) 1-4 bonds. In this respect chitin is similar to cellulose, with each alternate residue 'the other way up'.

These 'NAG' monomers are effectively glucose units with projecting N-acetyl amino groups attached to carbon 2, extending out sideways (to either side).

Polymerisation results in a long ribbon-like strand composed of hundreds or thousands of NAG subuits.

Chitin forms microfibrils with pairs of strands running parallel to one another, in opposite directions. This is stabilised by hydrogen bonds between -OH groups on the edge of glucose residues, and the acetyl groups.

Chitin is a component of fungal cell walls, and the exoskeleton (outer layer) of arthropods (crustaceans, insects). It is said to be the second most abundant polysaccharide in nature.