Chitin
Entomology · Mycology · Biochemistry
Say it: KYE-tin
Chitin is a tough, nitrogen-containing polysaccharide built from N-acetylglucosamine units that forms arthropod exoskeletons and fungal cell walls.
Definition
What is chitin?
Chitin is a long, unbranched chain of sugar units, each a molecule of N-acetylglucosamine: glucose in which one hydroxyl group has been replaced by a nitrogen-containing acetylamino group. The units are joined by beta 1-4 links, the same type of bond that holds cellulose together, so chitin is often described as a nitrogen-bearing version of cellulose. After cellulose, it is thought to be the most plentiful natural polymer on Earth.
Neighboring chitin chains bind tightly through hydrogen bonds, forming strong crystalline fibers that do not dissolve in water. In insects, crustaceans and other arthropods these fibers are woven with proteins into the cuticle, the exoskeleton, which crabs and lobsters stiffen further with calcium carbonate. Chitin is also a main component of fungal cell walls, and it occurs in squid beaks and pens and in the tubes of some marine worms. Vertebrates make no chitin, so some insecticides work by blocking its production in insects.
Industry extracts chitin from crab and shrimp shells and partly strips off its acetyl groups to make chitosan, a material used in wound dressings, drug delivery and water treatment.
Word parts
Where does the word “chitin” come from?
- chit-
- tunic, outer coveringGreek khiton
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Terms that go with it
- ExoskeletonAn exoskeleton is a hard external skeleton that supports and protects an animal's body, as in insects, spiders and crustaceans.
- ArthropodAn arthropod is an invertebrate animal with a segmented body, a hard exoskeleton containing chitin and jointed legs, such as an insect, spider or crab.
- FungusA fungus is a eukaryote, such as a yeast, mold or mushroom, that has chitin in its cell walls and feeds by absorbing nutrients from its surroundings.
- CelluloseCellulose is a strong, unbranched polysaccharide of glucose units joined by beta 1-4 bonds and the main structural material of plant cell walls.
- CarbohydrateA carbohydrate is a sugar or a chain of sugars, such as starch or cellulose, built from carbon, hydrogen and oxygen and used for energy and structure.
- Cell wallA cell wall is a rigid layer outside the plasma membrane of plant, fungal, algal and most bacterial cells that gives shape and stops them bursting.
Sources
Checked against
Written for biofideX in plain words, after checking these references:
- OpenStax Biology 2e, 3.2 Carbohydrates
- NCBI MeSH: Chitin
- Younes and Rinaudo, Chitin and Chitosan Preparation from Marine Sources (Marine Drugs, 2015)
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