Valine (Val) and lysine (Lys) are amino acids. The structures of these amino acids can be found in the Data Booklet. The isoelectric point of an amino acid is the pH at which it exists as a zwitterion. The isoelectric point of valine is 6.0. The isoelectric point of lysine is 9.7.

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

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