chitin

(noun)

a complex polysaccharide, a polymer of N-acetylglucosamine, found in the exoskeletons of arthropods and in the cell walls of fungi; thought to be responsible for some forms of asthma in humans

Related Terms

Examples of chitin in the following topics:

  • Phylum Arthropoda

    • Arthropods are the largest grouping of animals all of which have jointed legs and an exoskeleton made of chitin.
    • Arthropods also show the presence of an exoskeleton made principally of chitin, which is a waterproof, tough polysaccharide.
    • It is made up of two layers: the epicuticle, which is a thin, waxy, water-resistant outer layer containing no chitin; and the chitinous procuticle, which is beneath the epicuticle.
    • Chitin is a tough, flexible polysaccharide.

  • Chytridiomycota: The Chytrids

    • Like all fungi, chytrids have chitin in their cell walls, but one group of chytrids has both cellulose and chitin in the cell wall.

  • Types of Skeletal Systems

    • Arthropods, such as crabs and lobsters, have exoskeletons that consist of 30–50 percent chitin, a polysaccharide derivative of glucose that is a strong-but-flexible material.
    • Chitin is secreted by the epidermal cells.

  • Phylum Mollusca

    • Additionally, a tongue-like organ called a radula, which bears chitinous tooth-like ornamentation, is present in many species, serving to shred or scrape food.
    • The mantle (also known as the pallium) is the dorsal epidermis in mollusks; shelled mollusks are specialized to secrete a chitinous and hard calcareous shell.

  • Limits on Animal Size and Shape

    • As the tough and resistant outer cover of an arthropod, the exoskeleton may be constructed of a tough polymer, such as chitin, and is often biomineralized with materials, such as calcium carbonate.
    • The increasing thickness of the chitin necessary to support this weight limits most animals with an exoskeleton to a relatively-small size.

  • Carbohydrate Molecules

    • Starch, glycogen, cellulose, and chitin are primary examples of polysaccharides.
    • This exoskeleton is made of chitin, which is a polysaccharide-containing nitrogen.
    • Chitin is also a major component of fungal cell walls.

  • Fungi Cell Structure and Function

    • The rigid layers of fungal cell walls contain complex polysaccharides called chitin and glucans.
    • Chitin, also found in the exoskeleton of insects, gives structural strength to the cell walls of fungi.

  • Skin, Gills, and Tracheal Systems

    • The tracheal system, the most direct and efficient respiratory system in active animals, has tubes made of a polymeric material called chitin.

  • The Fossil Record as Evidence for Evolution

    • Fossils usually consist of the portion of the organisms that was partially mineralized during life, such as the bones and teeth of vertebrates or the chitinous or calcareous exoskeletons of invertebrates.

  • Basic Structures of Prokaryotic Cells

    • The composition of their cell walls also differs from the eukaryotic cell walls found in plants (cellulose) or fungi and insects (chitin).