| (i) \[{{H}_{3}}{{N}^{+}}-CH(C{{H}_{3}})C{{O}_{2}}H\] |
| (ii) \[{{H}_{2}}N-CH(C{{H}_{3}})CO_{2}^{-}\] |
| (iii) \[{{H}_{3}}{{N}^{+}}-CH(C{{H}_{3}})CO_{2}^{-}\] |
| (iv) \[{{H}_{2}}N-CH(C{{H}_{3}})C{{O}_{2}}H\] |
A) I and II
B) I and III
C) II and III
D) III and IV
Correct Answer: A
Solution :
Isoelectric point for neutral amino acids ranges from pH 5.5 to 6.3. Acidic amino acids have isoelectric point around 3 while basic amino acids have ranges from pH 7.6 to 10.8. At isoelectric point, amino acids exist as Zwitter ions. At low pH, it exists as cation and at high pH, it exists as anion. Hence, alanine (pH range 2-4) will exist as cation while alanine (pH range 9-11) will exist as anion. Acidic medium: \[{{H}_{3}}{{N}^{+}}-CH(C{{H}_{3}})C{{O}_{2}}H\] Basic medium: \[{{H}_{2}}N-CH(C{{H}_{3}})CO_{2}^{-}\]
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