Isoelectric Point
Isoelectric point (pI) of amino acid is pH at which:
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About This Question
- Subject
- chemistry
- Chapter
- biomolecules
- Topic
- isoelectric point
- Difficulty
- Medium
- Year
- 2025
Solution
Correct Answer:
Net charge zero (zwitterion predominates)
- Definition: The isoelectric point (pI) is the specific pH at which a molecule carries no net electrical charge.
- State: At this pH, the molecule exists almost entirely as a dipolar zwitterion (+H3N−CHR−COO−).
- Properties at pI:
- It does not migrate in an electric field (electrophoresis).
- Solubility is usually at its minimum because the molecule has no net charge to interact strongly with water.
- Calculation: For neutral amino acids, pI=(pKa1+pKa2)/2.
This medium difficulty chemistry question is from the chapter biomolecules, covering the topic of isoelectric point. It appeared in the 2025 exam.
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