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[proh-teen, -tee-in] /ˈproʊ tin, -ti ɪn/
Biochemistry. any of numerous, highly varied organic molecules constituting a large portion of the mass of every life form and necessary in the diet of all animals and other nonphotosynthesizing organisms, composed of 20 or more amino acids linked in a genetically controlled linear sequence into one or more long polypeptide chains, the final shape and other properties of each protein being determined by the side chains of the amino acids and their chemical attachments: proteins include such specialized forms as collagen for supportive tissue, hemoglobin for transport, antibodies for immune defense, and enzymes for metabolism.
the plant or animal tissue rich in such molecules, considered as a food source supplying essential amino acids to the body.
(formerly) a substance thought to be the essential nitrogenous component of all organic bodies.
Biochemistry. of the nature of or containing protein.
Also, proteid
[proh-teed, -tee-id] /ˈproʊ tid, -ti ɪd/ (Show IPA)
Origin of protein
1835-45; < German Protein < Greek prōte(îos) primary + German -in -in2; replacing proteine < French
Related forms
[proh-tee-ney-shuh s, -tee-i-ney-] /ˌproʊ tiˈneɪ ʃəs, -ti ɪˈneɪ-/ (Show IPA),
proteinic, proteinous, adjective
nonprotein, noun
Can be confused
protean, protein. Unabridged
Based on the Random House Dictionary, © Random House, Inc. 2018.
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Examples from the Web for proteins
Contemporary Examples
Historical Examples
  • Likewise, the proteins also pass through the liver on their way to the body.

    The Mother and Her Child William S. Sadler
  • Also that there are other proteins and that the protoplasm is not all nuclein.

    The Fundamentals of Bacteriology Charles Bradfield Morrey
  • Antigens were considered by Ehrlich to be proteins or to be related to proteins.

    The Fundamentals of Bacteriology Charles Bradfield Morrey
  • Protoplasm is rich in lipoids; probably it is mainly an emulsion of these and proteins.

  • The same eighteen acids are present in the proteins of all the higher animals.

    Physiology Ernest G. Martin
British Dictionary definitions for proteins


any of a large group of nitrogenous compounds of high molecular weight that are essential constituents of all living organisms. They consist of one or more chains of amino acids linked by peptide bonds and are folded into a specific three-dimensional shape maintained by further chemical bonding
Derived Forms
proteinaceous, proteinic, proteinous, adjective
Word Origin
C19: via German from Greek prōteios primary, from protos first + -in
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition
© William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins
Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012
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Word Origin and History for proteins



1844, from French protéine, coined 1838 by Dutch chemist Gerhard Johan Mulder (1802-1880), perhaps on suggestion of Berzelius, from Greek proteios "the first quality," from protos "first" (see proto-) + -ine (2).

Originally a theoretical substance thought to be essential to life, further studies of the substances he was working with overthrew this, but the words protein and proteid continued to be used in international work on the matter and also for other organic compounds; the modern use as a general name for a class of bodies arose in German. The confusion became so great a committee was set up in 1907 to sort out the nomenclature, which it did, giving protein its modern meaning and banishing proteid.

Online Etymology Dictionary, © 2010 Douglas Harper
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proteins in Medicine

protein pro·tein (prō'tēn', -tē-ĭn)
Any of a group of complex organic macromolecules that contain carbon, hydrogen, oxygen, nitrogen, and usually sulfur and are composed of chains of alpha-amino acids. Proteins are fundamental components of all living cells and include many substances, such as enzymes, hormones, and antibodies, that are necessary to the 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.

pro'tein·a'ceous (prōt'n-ā'shəs, prō'tē-nā'-) adj.
The American Heritage® Stedman's Medical Dictionary
Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.
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proteins in Science
Any of a large class of complex organic chemical compounds that are essential for life. Proteins play a central role in biological processes and form the basis of living tissues. They consist of long chains of amino acids connected by peptide bonds and have distinct and varied three-dimensional structures, usually containing alpha helices and beta sheets as well as looping and folded chains. Enzymes, antibodies, and hemoglobin are examples of proteins.

Our Living Language  : Proteins are the true workhorses of the body, carrying out most of the chemical processes and making up the majority of cellular structures. Proteins are made up of long chains of amino acids, but they don't resemble linear pieces of spaghetti. The atoms in these long chains have their own attractive and repulsive properties. Some of the amino acids can form bonds with other molecules in the chain, kinking and twisting and folding into complicated, three-dimensional shapes, such as helixes or densely furrowed globular structures. These folded shapes are immensely important because they define the protein's function in the cell. Some protein shapes fit perfectly in cell receptors, turning chemical processes on and off, like a key in a lock, whereas others work to transport molecules throughout the body (hemoglobin's shape is ideal for carrying oxygen). When proteins fail to take on their preordained shapes, there can be serious consequences: misfolded proteins have been implicated in diseases such as Alzheimer's, mad cow, and Parkinson's, among others. Exactly how proteins are able to fold into their required shapes is poorly understood and remains a fundamental question in biochemistry. See more at prion.
The American Heritage® Science Dictionary
Copyright © 2002. Published by Houghton Mifflin. All rights reserved.
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proteins in Culture
proteins [(proh-teenz, proh-tee-inz)]

Complex organic molecules made up of amino acids. Proteins are basic components of all living cells and are therefore among the principal substances that make up the body. In addition to being necessary for the growth and repair of the body's tissues, proteins provide energy and act as enzymes that control chemical reactions in the cell.

Note: Foods that contain a high percentage of protein include meat, fish, poultry, milk products, beans, and nuts.
The New Dictionary of Cultural Literacy, Third Edition
Copyright © 2005 by Houghton Mifflin Company.
Published by Houghton Mifflin Company. All rights reserved.
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