Amino Acid
Definition and meaning of Amino Acid in chemistry.
An amino acid is a small organic molecule containing both an amino group (−NH2) and a carboxyl group (−COOH) attached to a central alpha carbon, along with a variable side chain. Amino acids are the monomeric building blocks of proteins, linking together via peptide bonds to form polypeptides and proteins.
In more detail
The approximately 20 standard amino acids found in nature differ only in their side chains (R groups), which determine their chemical properties and behavior within proteins. Depending on pH, each amino acid exists in different protonation states, predominantly as zwitterions at physiological pH with both positive and negative charges. Amino acids are essential for virtually all biological functions, from catalyzing reactions as enzymes to providing structural support and regulating metabolism. The specific sequence of amino acids in a protein determines its three-dimensional structure and therefore its biological function.
Key facts
| Field | Biochemistry |
|---|---|
| General Structure | H2N−CHR−COOH (where R is the variable side chain) |
| Standard Amino Acids | Approximately 20 incorporated into proteins; over 500 others exist in nature |
| Linkage | Connected via peptide bonds (C−N covalent bonds between carboxyl and amino groups) |
Alanine is one of the simplest amino acids, with a methyl (−CH3) group as its side chain. It appears in nearly all proteins and plays important roles in muscle metabolism and glucose homeostasis through the glucose-alanine cycle.
Frequently asked questions
Why are amino acids called 'amino' acids?
They are named for their two defining functional groups: the amino group (−NH2) and the carboxyl acid group (−COOH) present on all amino acids.
Do amino acids only function as protein building blocks?
No; while best known in proteins, amino acids also serve as neurotransmitters, hormones, immune mediators, and intermediates in central metabolic pathways.