A neutral amino acid has two dissociation constants: for the carboxyl group and for the amino group. — Biomolecules Chemistry Question
Question
A neutral amino acid has two dissociation constants: $pK_{a1} = 2.3$ for the carboxyl group and $pK_{a2} = 9.7$ for the amino group. The exact isoelectric point ($pI$) of this amino acid is:
Answer: A
💡 Solution & Explanation
For a neutral amino acid without an ionizable side chain, the isoelectric point ($pI$) is the arithmetic mean of the two $pKa$ values. $pI = (2.3 + 9.7) / 2 = 12.0 / 2 = 6.0$.
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