keratin(redirected from hard keratin)
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keratin(kĕr`ətĭn), any one of a class of fibrous proteinprotein,
any of the group of highly complex organic compounds found in all living cells and comprising the most abundant class of all biological molecules. Protein comprises approximately 50% of cellular dry weight.
..... Click the link for more information. molecules that serve as structural units for various living tissues. The keratins are the major protein components of hair, wool, nails, horn, hoofs, and the quills of feathers. These proteins generally contain large quantities of the sulfur-containing amino acidsamino acid
, any one of a class of simple organic compounds containing carbon, hydrogen, oxygen, nitrogen, and in certain cases sulfur. These compounds are the building blocks of proteins.
..... Click the link for more information. , particulary cysteinecysteine
, organic compound, one of the 20 amino acids commonly found in animal proteins. Only the l-stereoisomer participates in the biosynthesis of mammalian protein.
..... Click the link for more information. . The helical keratin molecules twist around each other to form elongated strands called intermediate filaments. The formation of a covalent chemical bondchemical bond,
mechanism whereby atoms combine to form molecules. There is a chemical bond between two atoms or groups of atoms when the forces acting between them are strong enough to lead to the formation of an aggregate with sufficient stability to be regarded as an
..... Click the link for more information. called a disulfide bridge between the sulfer atoms on two cysteins on separate polypeptide chains of keratin allows for the cross-linkage of these chains and results in a fairly rigid aggregate. This phenomenon is seen to be consistent with the physiological role of the keratins, which provide a tough, fibrous matrix for the tissues in which they are found. Human hair is approximately 14% cystine (cysteins cross-linked by disulfide bridges).
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Any of various albuminoids characteristic of epidermal derivatives, such as nails and feathers, which are insoluble in protein solvents, have a high sulfur content, and generally contain cystine and arginine as the predominating amino acids.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.
A proteinaceous material used as a retarder for plaster.
McGraw-Hill Dictionary of Architecture and Construction. Copyright © 2003 by McGraw-Hill Companies, Inc.
a fibrous protein that occurs in the outer layer of the skin and in hair, nails, feathers, hooves, etc.
Collins Discovery Encyclopedia, 1st edition © HarperCollins Publishers 2005