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InterviewSolution
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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 `:`A. `6.62 & 9.74`B. `2.77 & 5.6`C. `2.77 & 9.74`D. `9.74 & 6.62` |
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Answer» Correct Answer - 3 For acidic amino acid. `P^(1)=(p^(Ka_(1))+p^(Ka_(3)))/(2)=(1.88+3.65)/(2)=(5.53)/(2)=2.77` For basic amino acids `P^(1)=(p^(Ka_(2))+p^(Ka_(3)))/(2)=(8.95+10.53)/(2)=(19.48)/(2)=9.74` |
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