Proteins: Structure and Functions · NCERT Biology

A particular property of amino acids is the ionizable nature of -NH2 and -COOH groups. In solutions of different pHs, the structure of amino acids changes. The form with both positive and negative charges is called:

  1. Anion (negative charge)
  2. Cation (positive charge)
  3. Zwitterion (dual charge)
  4. Non-polar (no charge)
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Correct answer: Zwitterion (dual charge)

The zwitterionic form occurs when the amino acid carries both a positive charge (on -NH3⁺) and a negative charge (on -COO⁻), resulting in a net neutral charge. This form predominates near the amino acid's isoelectric point.

Difficulty: Medium Question 12 of 20

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