• Contain carboxyl groups (weaker acids than α-carboxyl-group) • Negatively charged at physiological pH, present as conjugate bases (therefore –ate not –ic acids) • Carboxyl groups function as nucleophiles in some enzymatic reactions • Aspartate – • Glutamate – Acidic Amino Acids• Contain carboxyl groups (weaker acids than α-carboxyl-group) • Negatively charged at physiological pH, present as conjugate bases (therefore –ate not –ic acids) • Carboxyl groups function as nucleophiles in some enzymatic reactions • Aspartate – • Glutamate – Acidic Amino Acids