The 20 amino acids

Structures, codes, side-chain class and codons

These are the 20 amino acids the standard genetic code assigns to codons. Each structure is drawn the same way: amino group left, carboxyl group right, side chain up, neutral form, L-configuration at the alpha carbon. The class follows the common five-class scheme from biochemistry textbooks; books differ on glycine, proline, cysteine, histidine and tyrosine. Codons are written as mRNA (U instead of T).

Practice the 20 amino acids Practice codons Practice pathways

StructureName3-letter1-letterSide-chain classCodons
AlanineAlaANonpolar, aliphaticGCU GCC GCA GCG
CysteineCysCPolar, unchargedUGU UGC
Aspartic acidAspDNegatively chargedGAU GAC
Glutamic acidGluENegatively chargedGAA GAG
PhenylalaninePheFAromaticUUU UUC
GlycineGlyGNonpolar, aliphaticGGU GGC GGA GGG
HistidineHisHPositively chargedCAU CAC
IsoleucineIleINonpolar, aliphaticAUU AUC AUA
LysineLysKPositively chargedAAA AAG
LeucineLeuLNonpolar, aliphaticUUA UUG CUU CUC CUA CUG
MethionineMetMNonpolar, aliphaticAUG
AsparagineAsnNPolar, unchargedAAU AAC
ProlineProPNonpolar, aliphaticCCU CCC CCA CCG
GlutamineGlnQPolar, unchargedCAA CAG
ArginineArgRPositively chargedCGU CGC CGA CGG AGA AGG
SerineSerSPolar, unchargedUCU UCC UCA UCG AGU AGC
ThreonineThrTPolar, unchargedACU ACC ACA ACG
ValineValVNonpolar, aliphaticGUU GUC GUA GUG
TryptophanTrpWAromaticUGG
TyrosineTyrYAromaticUAU UAC