Question

The pKa of the α‑carboxyl group of serine is 2.21 , and the pKa of its α‑amino group is 9.15 . Calculate the average net charge on serine if it is in a solution that has a pH of 8.30 .

Answer 1

Answer:

Net charge in serine at pH equal to 8.30 is "0"

Explanation:

• At pH > $pK_{a}$, carboxyl group exists as $-CO_{2}^{-}$ (charged)

• At pH < $pK_{a}$, carboxyl group exists as -COOH (neutral)
• At pH > $pK_{a}$, amino group exists as $-NH_{2}$ (neutral)
• At pH < $pK_{a}$, amino group exists as $-NH_{3}^{+}$ (charged)
• So, at pH = 8.30, both carboxyl and amino group exists in charged state.
• Net charge in serine at pH equal to 8.30 is "0".
• Structure of serine at pH equal to 8.30 has been shown below.