Serine (abbreviated as
Ser or
S) encoded by the
codons UCU, UCC, UCA, UCG, AGU and AGC is an ɑ-amino acid that is used in the biosynthesis of proteins. It contains an α-
amino group (which is in the
protonated − form under biological conditions), a
carboxyl group (which is in the
deprotonated – form under biological conditions), and a side chain
hydroxyl group, classifying it as a
polar amino acid. It is non-essential in humans, meaning the body can synthesize it.