BIOL 103 Lecture Notes - Lecture 6: Magnesium Carbonate, Phosphocreatine, Hydrolysis
20 Jun 2016
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Document Summary
Hard encasement on the animal"s surface, mostly made of calcium carbonate secreted by the mantle (sheet-like extension of the body"s wall) Close hinged shell by using muscles attached to the inside of the exoskeleton, and as animal grows, adds to outer edge of shell to enlarge it. Insects and arthropods= jointed exoskeleton called a cuticle (nonliving coat secreted by the epidermis) Cuticle consists of chitin, and fibrils of chitin are in a protein matrix= composite material for strength and flexibility. Cuticle can be hardened with organic compounds that cross-link the proteins of the matrix ex: crustaceans like lobsters, calcium salts are added. Cuticle remains unharden if body part needs to be flexible and muscles attach to knobs and plates of cuticle extend to the interior of the body. Each time it grows, arthropod sheds the exoskeleton (moult) to make a larger one. Ex: sponges, consist of hard needle-like structures of inorganic material or fibres made of proteins.
