Ammino acids

Amino acids having both the amine and carboxylic acid groups attached to the first (alpha-) carbon atom have particular importance in biochemistry. They are known as 2-, alpha-, or α-amino acids ;^[4] often the term "amino acid" is used to refer specifically to these. They include the 23 proteinogenic ("protein-building") amino acids which combine into peptide chains ("polypeptides") to form the building blocks of a vast array of proteins.^[5] These are all L-stereoisomers ("left-handed" isomers) although a few D-amino acids ("right-handed") occur in bacterial envelopes and some antibiotics.^[6][7] 20 of the 23 proteinogenic amino acids are encoded directly by triplet codons in the genetic code and are known as "standard" amino acids. The other three ("non-standard" or "non-canonical") are pyrrolysine , selenocysteine (present in many noneukaryotes as well as most eukaryotes), and N-Formylmethionine. For example, 25 human proteins include selenocysteine (Sec) in their primary structure,^[8] and the structurally characterized enzymes (selenoenzymes) employ Sec as the catalytic moiety in their active sites.^[9] Pyrrolysine and selenocysteine are encoded via variant codons; for example, selenocysteine is encoded by stop codon and SECIS element.Codon–tRNA combinations not found in nature can also be used to "expand" the genetic code and create novel proteins known as alloproteins incorporating non-proteinogenic amino acids
Many important proteinogenic and non-proteinogenic amino acids also play critical non-protein roles within the body.Essential amino acids may also differ between species.^[17]
Because of their biological significance, amino acids are important in nutrition and are commonly used in nutritional supplements, fertilizers, and food technology. Industrial uses include the production of drugs, biodegradable plastics and chiral catalysts.


Source::  en.wikipedia.org/wiki/Amino_acid‎