is one of the main components in the cell walls of fungi
, the exoskeleton
and other arthropods
, and in some other animals. It is a polysaccharide
, made out of units of acetylglucosamine (more completely, N-acetyl-D-glucos-2-amine). These are linked together in β-1,4 fashion, the same as the glucose
units that make up cellulose
. So chitin may be thought of as cellulose
, with one hydroxyl
group on each monomer
replaced by an acetylamino
group. This allows for increased hydrogen
bonding between adjacent polymers
, giving the material increased strength.
"Chitin" and "chiton" (a marine animal) both derive from the same Greek word meaning "tunic", referring to the hardness.