a hormone Various antibiotics are amino acid derivatives (penicillin). Acid-base Chemistry of Amino AcidsAmino acids by themselves have amino (pKa ~9.0-10.5) and carboxyl groups (pKa ~2.0-2.4) that can be titrated At neutral pH the amino group is protonated, and the carboxyl group is canadian-pharmacyv.com viagra legal online kaufen