protein defined in 1951 yearprotein - protein;
protein - Very complex organic compound, composed of numerous amino-acids. Proteins of innumerably many different kinds are present in all living things, making a considerable proportion of their dry weight. A protein molecule is made of hundreds or thousands of ammo-acid molecules joined together by peptide links into one or more chains, which are variously folded. There are 20 different kinds of ammo-acid commonly found in proteins, and most of these usually occur in any one protein molecule; they are arranged in the chain in a sequence which is exactly the same in all molecules of a given kind of protein. The possible different arrangements of the amino-acids are evidently practically infinite, and the diversity is fully exploited by living things, every species having kinds of protein molecule peculiar to itself. A protein molecule is very large (most have a molecular weight from about 20,000 up to several million), and dissolved proteins form therefore colloidal solutions. Proteins are not soluble in fat solvents. Many are soluble in water or dilute salt solutions (e.g. globulins); others, with elongated (fibrous) molecules, are insoluble in these solvents (e.g. scleroproteins, myosin). Proteins are synthesized from amino-acids by all living things; the precise sequence of the amino-acids being determined by the sequence of nucleotides in nucleic acids. Only autotrophic organisms make them from inorganic substances. They are destroyed by proteolytic enzymes (See also: Peptone, Polypeptide). Proteins are frequently combined with other substances, especially nucleic acid (nucleo-proteins), carbohydrates (muco- or glycoproteins), fats (lipoproteins).
near protein in Knolik
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