Amino acid/List of amino acids

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The 20 amino acids used in the translation (synthesis of proteins):

Amino acid Nucleotide triplett(s) Essential?a Chiral?b
Alanine GCU, GCC, GCA, GCG No Yes
Arginine CGU, CGC, CGA, CGG, AGA, AGG No[note 1] Yes
Asparagine AAU, AAC No Yes
Aspartic acid GAU, GAC No Yes
Cysteine UGU, UGC No[note 2] Yes
Glutamine CAA, CAG No Yes
Glutamic acid GAA, GAG No Yes
Glycine GGU, GGC, GGA, GGG No No
Histidine CAU, CAC Yes Yes
Isoleucine AUU, AUC, AUA Yes Yes
Leucine UUA, UUG, CUU, CUC, CUA, CUG Yes Yes
Lysine AAA, AAG Yes Yes
Methionine[note 3] AUG Yes Yes
Phenylalanine UUC, UUU Yes Yes
Proline CCU, CCC, CCA, CCG No Yes
Serine UCU, UCC, UCA, UCG, AGC, AGU No Yes
Threonine ACU, ACC, ACA, ACG Yes Yes
Tryptophan UGG Yes Yes
Tyrosine UAC, UAU No Yes
Valine GUU, GUC, GUA, GUG Yes Yes

a Essential in this context means that the amino acids must be consumed as part of the human diet, they cannot be made (in humans) by converting one amino acid into another.

b Technical word for "looks like a pair of gloves" (chiral molecules are like gloves in that they are made from all the same parts, but are mirror images of each other)

Two special amino acids:

Amino acid Nucleotide triplett(s) Essential? Chiral?
Selenocysteine UGA No[note 4] Yes
Pyrrolysine UAG[note 5] N/A Yes

Works cited[edit]


  1. If you're an adult, it is not essential.
  2. Cysteine can be essential in rare cases, but is usually not.
  3. Starts the amino acid chain.
  4. Selenocysteine is produced in humans. Normally, UGA means "stop", but through a complicated process, it will code for selenocysteine.
  5. No, this isn't a mistake. Pyrrolysine is used in bacteria, not humans, where it is coded for using UAG.