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

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Etymology

Origin of amino acid

First recorded in 1895–1900

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Compare meaning

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

• nucleic acid vs. amino acid

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Example Sentences

See Examples For:

amino acid

When Menin levels declined, the researchers noticed that concentrations of D-serine, an amino acid involved in brain signaling, also fell.

From Science Daily ● Oct. 12, 2026

For example, amino acid molecules, the building blocks of proteins, exist as two forms that are each other's mirror image.

From BBC ● Oct. 7, 2026

The compound acts on a specific amino acid within the protein, triggering a pathway associated with cardiovascular benefits.

From Science Daily ● Sep. 28, 2026

Restoring that protein, called Menin, improved several signs of aging, while a separate treatment with the amino acid D-serine improved cognition.

From Science Daily ● Sep. 18, 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

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