alleryStart learning →Amino acids exist predominantly as zwitterions (⁺NH₃-CHR-COO⁻) at:
- All pH
- Strong acid
- Strong base
- Isoelectric point (pI) — pH where net charge is zero
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Correct answer: D. Isoelectric point (pI) — pH where net charge is zero
**At pI:** -NH₂ protonated to -NH₃⁺ and -COOH deprotonated to -COO⁻
net charge = 0. For glycine pI ≈ 6.0. At lower pH: protonated (net +)
higher pH: deprotonated (net -).
Amino acids have high mp (ionic-like solid).