Chapter 19, Problem 19.65P

For each amino acid $\left[\text{RCH}\left({\text{NH}}_{\text{2}}\right)\text{COOH}\right]$, draw its neutral, positively charged, and negatively charged forms. Which form predominates at $\text{pH}=\text{1, 6}$ and $11$? What is the structure of each amino acid at its isoelectric point?

a. methionine $\left(\text{R}={\text{CH}}_{\text{2}}{\text{CH}}_{\text{2}}{\text{SCH}}_{\text{3}}\right)$

b. serine $\left(\text{R}={\text{CH}}_{\text{2}}\text{OH}\right)$