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amino acid

The term "amino" in amino acid means the amino group (-NH-), and "acid" means the carboxyl group (-CO-), respectively. That is, the name of the amino acid is derived from it's property including both features.

Basically, there are only twenty kinds of amino acids used in natural proteins. Each amino acid consists of two parts, the backbone (-NH-C-CO-) which is common in all amino acids, and the sidechain which is different in each amino acid.

The feature of each amino acid is described below.

The color of each atom is described below:

grey blue red white yellow
carbon(C) nitrogen(N) oxygen(O) hydrogen(H) sulfur(S)
  • no sidechain
    GLY
    glycine
    The glycine is the only amino acid in all the twenty amino acids without sidechain.
  • negative charged
    ASP GLU
    aspartic acid glutamic acid
  • positive charged
    ARG LYS
    arginine leucine
  • polar
    ASN GLN SER THR
    asparagine glutamine serine threonine
    HIS
    histidine
  • hydrophobic
    LEU ILE VAL MET
    leucine isoleucine valine methionine
    CYS PHE TYR TRP
    cysteine phenylalanine tyrosine tryptophan
  • others
    ALA PRO
    alanine proline

The alanine has only one methyl group as it's sidechain. The proline composes a covalent bond between the tip of sidechain and amino group of backbone in it's molecule.