Each ionizable group of an amino acid can exist in one of two states, charged or neutral. The electric charge on the functional group is determined by the relationship between its pKa and the pH of the solution. This relationship is described by the Henderson-Hasselbalch equation. Lysine has three ionizable functional groups. The pKa for these groups are pK1 = 3.1, pK2 = 8.3 and pKR = 10.8. 1. Draw the structures of the predominant ionization state of Lysine at pH 1, 4, 8, and 12. Calculate also the net charge of each of these ionized molecules. Show your work. 2. Calculate the isoelectric point (pI) of Lysine in aqueous solution using the pKa values given above. Explain the rationale of your calculations and show your work.

Biochemistry
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Author:Lubert Stryer, Jeremy M. Berg, John L. Tymoczko, Gregory J. Gatto Jr.
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Chapter1: Biochemistry: An Evolving Science
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Each ionizable group of an amino acid can exist in one of two states, charged or neutral. The electric charge on the functional group is determined by the relationship between its pKa and the pH of the solution. This relationship is described by the Henderson-Hasselbalch equation. Lysine has three ionizable functional groups. The pKa for these groups are pK1 = 3.1, pK2 = 8.3 and pKR = 10.8.

1. Draw the structures of the predominant ionization state of Lysine at pH 1, 4, 8, and 12. Calculate also the net charge of each of these ionized molecules. Show your work.

2. Calculate the isoelectric point (pI) of Lysine in aqueous solution using the pKa values given above. Explain the rationale of your calculations and show your work.

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