CH 3-5: pH, pKa and Acid/Base Structure The aqueous pH will effect the structure of an acid or base. This can effect a compounds solubility and even biological activity and mobility. What is the acid/base structure of the amino acid Lysine at physiological pH? (~pH 7.4)

Acid/Base Structure of Lysine at pH 7.4 If the pH > pKa for a specific acidic functional group, this group is said to be in a basic environment, and will exist in its basic form (Conjugate Base). If the pH < pKa for a specific acidic functional group, this group is said to be in an acidic environment, and will remain in its acid form. pKa 5.2 pKa ~ 10 pKa ~ 9 Structure of Lysine at pH 7.4:

What is the acid/base structure of the amino acid cysteine at pH 11? pKa ~ 8 pKa 5.2 pKa ~ 9 Structure of Functional Groups depends on pH: If pH>pKa…functional group is in its base form. If pH<pka…functional group is in its acid form.