An amino acid is characterized by two `pKa` values the one corresponding to the more acidic site is designated as `pKa_(1)` and the other corresponding to the less site is designated as `pKa_(2)`. Some amino acids have side chain with acidic or basic groups. These amino acids have `pKa_(3)` value also for the side chain.
`|{:(S.No,"Amino acid",P^(Ka1),P^(Ka2),P^(Ka3)" (Side chain)"),(I,"Aspartic acid",1.88,9.6,3.65),(II,"Glutamic acid",2.19,9.67,4.25),(III,"Lysine",2.18,8.95,10.53),(IV,"Arginine",2.17,9.04,12.48):}|`
The isoelectric point `(pI)` of Aspartic acid and lysine will be respectively `:`

Options

A. 6.62
B. 5.74
C. 2.77
D. 9.74

Answer

C

Explanation

For acidic amino acid.
`P^1=(P^(Ka_1)+P_(Ka_3))/2=(1.88+3.65)/2=5.53/2=2.77`