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nettle

(Encyclopedia)nettle, common name for the Urticaceae, a family of fibrous herbs, small shrubs, and trees found chiefly in the tropics and subtropics. Several genera of nettles are covered with small stinging hairs ...

parathyroid hormone

(Encyclopedia)parathyroid hormone or parathormone, a hormone secreted by the parathyroid glands that regulates the metabolism of calcium and phosphate in the body. It has been purified extensively and appears to be...

pepsin

(Encyclopedia)pepsin, enzyme produced in the mucosal lining of the stomach that acts to degrade protein. Pepsin is one of three principal protein-degrading, or proteolytic, enzymes in the digestive system, the othe...

Adirondack Mountains

(Encyclopedia)Adirondack Mountains ădˌərŏnˈdăk [key], mountain mass, NE N.Y., between the St. Lawrence valley in the north and the Mohawk valley in the south; rising to 5,344 ft (1,629 m) at Mt. Marcy, the hi...

Wolfe, Tom

(Encyclopedia)Wolfe, Tom (Thomas Kennerly Wolfe, Jr.), 1931–2018, American journalist and novelist, b. Richmond, Va., B.A. Washington and Lee Univ., 1951, Ph.D. Yale, 1957. He began his writing career as a newspa...

caffeine

(Encyclopedia)caffeine kăfēnˈ [key], odorless, slightly bitter alkaloid found in coffee, tea, kola nuts (see cola), ilex plants (the source of the Latin American drink maté), and, in small amounts, in cocoa (se...

adsorption

(Encyclopedia)adsorption, adhesion of the molecules of liquids, gases, and dissolved substances to the surfaces of solids, as opposed to absorption, in which the molecules actually enter the absorbing medium (see a...

sprue

(Encyclopedia)sprue, chronic disorder of the small intestine caused by impaired absorption of fat and other nutrients. Two forms of the disease exist. Tropical sprue occurs in central and northern South America, As...

thyroxine

(Encyclopedia)thyroxine thīrŏkˈsēn [key], substance secreted by the thyroid gland. The hormone thyroxine forms by combining the amino acid tyrosine with iodine. Complexed to a protein, it is stored in the folli...

silica

(Encyclopedia)silica or silicon dioxide, chemical compound, SiO2. It is insoluble in water, slightly soluble in alkalies, and soluble in dilute hydrofluoric acid. Pure silica is colorless to white. It occurs in sev...