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amino acid

American  
[uh-mee-noh as-id] / əˈmi noʊ ˈæs ɪd /

noun

Biochemistry.
  1. any of a class of organic compounds that contains at least one amino group, –NH 2 , and one carboxyl group, –COOH: the alpha-amino acids, RCH(NH2 )COOH, are the building blocks from which proteins are constructed.


amino acid British  

noun

  1. any of a group of organic compounds containing one or more amino groups, -NH 2 , and one or more carboxyl groups, -COOH. The alpha-amino acids RCH(NH 2 )COOH (where R is either hydrogen or an organic group) are the component molecules of proteins; some can be synthesized in the body ( nonessential amino acids ) and others cannot and are thus essential components of the diet ( essential amino acids )

"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

amino acid Scientific  
  1. Any of a large number of compounds found in living cells that contain carbon, oxygen, hydrogen, and nitrogen, and join together to form proteins. Amino acids contain a basic amino group (NH 2) and an acidic carboxyl group (COOH), both attached to the same carbon atom. Since the carboxyl group has a proton available for binding with the electrons of another atom, and the amino group has electrons available for binding with a proton from another atom, the amino acid behaves as an acid and a base simultaneously. Twenty of the naturally occurring amino acids are the building blocks of proteins, which they form by being connected to each other in chains. Eight of those twenty, called essential amino acids, cannot be synthesized in the cells of humans and must be consumed as part of the diet. The remaining twelve are nonessential amino acids.


Etymology

Origin of amino acid

First recorded in 1895–1900

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Example Sentences

Examples are provided to illustrate real-world usage of words in context. Any opinions expressed do not reflect the views of Dictionary.com.

They then measured how each amino acid influenced regeneration in intestinal stem cells.

From Science Daily • May 21, 2026

The human body can also produce cysteine on its own by converting another amino acid called methionine in the liver.

From Science Daily • May 21, 2026

With the amino acid mixture, efficiency climbed to between 85 and 90 percent after a single dose.

From Science Daily • Apr. 20, 2026

That’s despite few clinical studies supporting the effectiveness or safety of these peptides, which are amino acid chains meant to help regulate functions in the body and have become popular among fitness and longevity enthusiasts.

From Salon • Apr. 4, 2026

The alteration of the single amino acid was discovered by Vernon Ingram, a former student of Max Perutz’s.

From "The Gene" by Siddhartha Mukherjee

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