Within the list shown below, the correct pair of structures of alanine in pH ranges 2-4 and 9-11 is (I) H3N+ - CH(CH3)CO2H (II) H2N - CH(CH3)CO2 - (II) H3N+ - CH(CH3)CO2 - (IV) H2N - CH(CH3)CO2H

Question

Within the list shown below, the correct pair of structures of alanine in pH ranges 2-4 and 9-11 is (I) H3N+ - CH(CH3)CO2H (II) H2N - CH(CH3)CO2 - (II) H3N+ - CH(CH3)CO2 - (IV) H2N - CH(CH3)CO2H (A) I and II (B) I, and III (C) II and III (D) III and IV

Tardigrade Admin · Accepted Answer

Isoelectric point for neutral amino acids ranges from

p H 5.5

to 6.3. Acidic amino acids have isoelectric point around 3 while basic amino acids have ranges from

p H 7.6

to

10.8

.
At isoelectric point, amino acids exist as Zwitter ions. At low

p H

, it exists as cation and at high

p H

, 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^{+} - C H (C H_{3}) C O_{2} H

Basic medium:

H_{2} N - C H (C H_{3}) C O_{2}^{-}

Q. Within the list shown below, the correct pair of structures of alanine in pH ranges 2−4 and 9−11 is (I) H3​N+−CH(CH3​)CO2​H (II) H2​N−CH(CH3​)CO2−​ (II) H3​N+−CH(CH3​)CO2−​ (IV) H2​N−CH(CH3​)CO2​H

I and II

I, and III

II and III

III and IV

Q. Within the list shown below, the correct pair of structures of alanine in $p H$ ranges $2 - 4$ and $9 - 11$ is
(I) $H_{3} N^{+} - C H (C H_{3}) C O_{2} H$
(II) $H_{2} N - C H (C H_{3}) C O_{2}^{-}$
(II) $H_{3} N^{+} - C H (C H_{3}) C O_{2}^{-}$
(IV) $H_{2} N - C H (C H_{3}) C O_{2} H$