Tyrosine (Tyr, Y) – Polar side chain: (4-Hydroxyphenyl)methyl group.

An aromatic amino acid.  The phenolic hydrogen of the side chain is ionizable at elevated pH (pK_a 10.1).  Note that delocalization of negative charge in the phenoxide ion allows deprotonation at lower pH than for the aliphatic alcohol side chains (Ser & Thr pK_a's ~13).