Amino acid
Say it: uh-MEE-noh AS-id
An amino acid is a small organic molecule with an amino group, a carboxyl group and a side chain; amino acids link together to form proteins.
Also: amino acids, alpha-amino acid
Definition
What is an amino acid?
An amino acid is an organic compound that carries both an amino group (-NH2) and a carboxyl group (-COOH). In the amino acids that build proteins, both groups are attached to the same central carbon, the alpha carbon, along with a hydrogen atom and a variable side chain called the R group. The R group is what makes each amino acid different, giving it properties such as being polar, nonpolar, acidic or basic.
Cells use 20 standard amino acids, each encoded by one or more three-base codons in the genetic code, and join them through peptide bonds into polypeptide chains. The chemistry of the side chains determines how a chain folds and therefore how the finished protein works. In nutrition, nine amino acids are called essential for humans because the body cannot make them and must get them from food; the others can be built from different molecules.
Beyond protein building, amino acids can be broken down for energy and serve as raw material for other molecules, including some hormones and neurotransmitters such as serotonin, which is made from tryptophan.
Word parts
Where does the term “amino acid” come from?
- amino
- containing the -NH2 groupfrom amine, coined from ammonium
- acid
- sourLatin acidus
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Terms that go with it
- ProteinA protein is a large molecule made of one or more chains of amino acids, folded into a specific shape that determines its job in the body.
- Peptide bondA peptide bond is the covalent link that joins the carboxyl group of one amino acid to the amino group of the next, releasing a water molecule.
- CodonA codon is a sequence of three nucleotides in DNA or messenger RNA that stands for one amino acid or tells the ribosome to stop.
- TranslationTranslation is the process in which a ribosome reads the codons of a messenger RNA and links amino acids in that order to build a protein.
- MacronutrientA macronutrient is a nutrient needed in large amounts, namely carbohydrate, protein or fat, which together supply energy and the raw materials for growth.
- SerotoninSerotonin is a chemical messenger made from tryptophan that acts as a neurotransmitter in the brain and as a signal in the gut and blood.
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