(a)[1]
Draw the structure of valine at $\text{pH }6.0$.
(b)[3]
A solution of lysine is made with $\text{pH }9.7$. Dilute sulfuric acid is added slowly until the pH of the solution reaches $1.0$. The sulfuric acid reacts with lysine to form different organic ions that are not present in significant concentrations at $\text{pH }9.7$. Draw the structures of three of the organic ions that are produced during the addition of sulfuric acid in the boxes. Draw the organic ion present at $\text{pH }1.0$ in box C.
(c)[2]
Draw the structure of the dipeptide Val-Lys. The peptide bond should be shown in full.