amino acid

noun

: an amphoteric organic acid containing the amino group NH2
especially : any of the various amino acids having the amino group in the alpha position that are the chief components of proteins and are synthesized by living cells or are obtained as essential components of the diet

Examples of amino acid in a Sentence

Recent Examples on the Web
Examples are automatically compiled from online sources to show current usage. Read More Opinions expressed in the examples do not represent those of Merriam-Webster or its editors. Send us feedback.
However, matcha’s high levels of L-theanine, a calming amino acid, help balance caffeine’s stimulating effects. Jillian Kubala, Health, 19 Oct. 2025 More than 10% of the original amino acids remained intact after the simulated 50-million-year exposure, while those in the soil mixture degraded 10 times faster and did not survive. Samantha Mathewson, Space.com, 17 Oct. 2025 In a study conducted on mice, scientists from the Massachusetts Institute of Technology (MIT) found that cysteine, a sulfur-containing amino acid, had the strongest rejuvenating effect on stem cells and early-stage intestinal cells, which are often damaged during radiation therapy for cancer. Deirdre Bardolf, FOXNews.com, 16 Oct. 2025 In addition, dietary tryptophan – an amino acid found in foods such as poultry, eggs, tofu and seeds – is metabolized into compounds that activate the aryl hydrocarbon receptor, further boosting Treg cell activity and protecting against gut inflammation. Mitzi Nagarkatti, The Conversation, 10 Oct. 2025 See All Example Sentences for amino acid

Word History

First Known Use

1897, in the meaning defined above

Time Traveler
The first known use of amino acid was in 1897

Browse Nearby Words

Cite this Entry

“Amino acid.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/amino%20acid. Accessed 20 Oct. 2025.

Kids Definition

amino acid

noun
ami·​no acid
ə-ˈmē-nō-
: any of numerous acids that include some which are the building blocks of proteins and are made by living cells from simpler compounds or are obtained in the diet

Medical Definition

amino acid

noun
: an amphoteric organic acid containing the amino group NH2
especially : alpha-amino acid

More from Merriam-Webster on amino acid

Last Updated: - Updated example sentences
Love words? Need even more definitions?

Subscribe to America's largest dictionary and get thousands more definitions and advanced search—ad free!