Question 20.1: Draw the structural form of the amino acid alanine that pred......
Draw the structural form of the amino acid alanine that predominates in solution at each of the following pH values.
a. pH = 1.0
b. pH = 7.0
c. pH = 11.0
At low pH, both amino and carboxyl groups are protonated. At high pH, both groups have lost their protons. At neutral pH, the zwitterion is present.
a. \underset{ \quad\quad } {\begin{matrix} H \ \ \ \\ H_{3}\overset{+}{N}-\overset{|}{\underset{|}{C}}-COOH \\ CH_{3} \\ pH = 1.0 \\ (net \ charge \ of \ +1) \end{matrix}} b. \underset{ \quad} {\begin{matrix} H \ \ \\ H_{3}\overset{+}{N}-\overset{|}{\underset{|}{C}}-COO^{-} \\ CH_{3} \\ pH = 7.0 \\ (no \ net \ charge) \end{matrix}} c. \underset{ \quad\quad } {\begin{matrix} H \ \ \\ H_{2}N-\overset{|}{\underset{|}{C}}-COO^{-} \\ CH_{3} \\ pH = 11.0 \\ (net \ charge \ of \ -1) \end{matrix}}