Any of a group of complex organic macromolecules
that contain carbon, hydrogen, oxygen, nitrogen, and usually sulfur and are composed
of one or more chains of amino acids. Proteins
are fundamental components of all living cells and include many substances, such
as enzymes, hormones, and antibodies,
that are necessary for the proper functioning of an organism. They are essential
in the diet of animals for the growth and repair of tissue and can be obtained
from foods such as meat, fish, eggs, milk, and legumes.
Excerpted from The American Heritage Dictionary of the English Language, Third
Edition Copyright © 1992 by Houghton Mifflin Company. Electronic version
licensed from Lernout & Hauspie Speech Products N.V., further reproduction
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