protein Meaning, Definition & Usage

noun any of a large group of nitrogenous organic compounds that are essential constituents of living cells; consist of polymers of amino acids; essential in the diet of animals for growth and for repair of tissues; can be obtained from meat and eggs and milk and legumes
- a diet high in protein

Gr. prw^tos first: cf. prwtei^on the first place.

(Physiol. Chem.) A body now known as alkali albumin, but originally considered to be the basis of all albuminous substances, whence its name. This definition is no longer used. Proetin is now defined as any polymer of an amino acid joined by peptide (amide) bonds. Most natural proteins have alpha-amino acids as the monomeric constituents. All classical enzymes are composed of protein, and control most of the biochemical transformations carrie dout in living cells. They may be soluble, as casein, albumins, and other globular proteins, or insoluble (e. g. "structural proteins"), as collagen or keratin. "albumin", an older term for protein, is now used primarily to refer to certain specific soluble globular proteins found in eggs or blood serum, e.g. Bovine serum albumin, used as an enzymatically inert protein in biochemical research.