An amino acid is dissolved in a solution whose pH is below its isoelectric point (pI). What is its net charge?
Answer and explanation
Correct answer: B. Positive
- Step 1: At a pH below the pI the solution has excess protons, so the amino and carboxyl groups are mostly protonated. Step 2. The net charge is positive. Answer: positive. Why not the others: it would be negative above the pI and neutral exactly at the pI.
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