Amino acid - Wikipedia, the free encyclopedia


** Amino acid **

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This article is about the class of chemicals. For the structures and
properties of the standard proteinogenic amino acids, see Proteinogenic
amino acid.
The generic structure of an alpha amino acid in its un-ionized form
Table of Amino Acids.
The 21 amino acids found in eukaryotes, grouped according to their
side-chains' pK[a] values and charges carried at physiological pH 7.4

*Amino acids* (/əˈmiːnoʊ/, /əˈmaɪnoʊ/, or
/ˈæmɪnoʊ/) are biologically important organic compounds made
from amine (-NH[2]) and carboxylic acid (-COOH) functional groups, along
with a side-chain specific to each amino acid. The key elements of an amino
acid are carbon, hydrogen, oxygen, and nitrogen, though other elements are
found in the side-chains of certain amino acids. About 500 amino acids are
known^[1] and can be classified in many ways. Structurally they can be
classified according to the functional groups' locations as alpha- (α-),
beta- (β-), gamma- (γ-) or delta- (δ-) amino acids; other
categories relate to polarity, pH level, and side chain group type
(aliphatic, acyclic, aromatic, containing hydroxyl or sulfur, etc.) In the
form of proteins, amino acids comprise the second largest component (after
water) of human muscles, cells and other tissues.^[2] Outside proteins,
amino acids perform critical roles in processes such as neurotransmitter
transport and biosynthesis.

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* (generic formula
H[2]NCHRCOOH in most cases^[3] where R is an organic substituent known as a
"side-chain");^[4] often the term "amino acid" is used to refer
specifically to these. They include the 23 proteinogenic
("protein-building") amino acids


what are amino acids

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