amino acid

American  

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

noun

Biochemistry.

amino acids plural

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.

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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 )

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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.

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Other Word Forms

Noun Inflected Forms

• amino acids
  plural

Etymology

Origin of amino acid

First recorded in 1895–1900

Compare meaning

How does amino-acid compare to similar and commonly confused words? Explore the most common comparisons:

• nucleic acid vs. amino acid

Example Sentences

This combination allowed the researchers to look beyond correlations and gain stronger evidence about whether amino acid levels could directly influence lifespan.

From Science Daily • Jun. 15, 2026

Instead, the study focused on naturally occurring blood levels of the amino acid and how those levels were associated with longevity.

From Science Daily • Jun. 15, 2026

In experiments with mice, restoring the protein reversed several signs of aging, while a simple amino acid supplement improved cognitive function.

From Science Daily • May 24, 2026

One ongoing project is examining whether the amino acid can stimulate hair follicle repair and regrowth.

From Science Daily • May 21, 2026

A change in a single DNA nucleotide causes a change in a single amino acid in the protein for which that DNA codes.

From "Cosmos" by Carl Sagan