For the amino acid glycine (), the successive acid dissociation constants are analytically given as (for the group) and (for the group). At what precise pH will the molecule exist primarily as an elec

Question

For the amino acid glycine ($NH_2CH_2COOH$), the successive acid dissociation constants are analytically given as $pK_{a1} = 2.18$ (for the $-COOH$ group) and $pK_{a2} = 8.96$ (for the $-NH_3^+$ group). At what precise pH will the molecule exist primarily as an electrically neutral zwitterion (the isoelectric point)?

Prashant Kotian · Accepted Answer

Correct answer: A. The isoelectric point () of a completely neutral amino acid is the pH at which it carries virtually no net electrical charge. This specific pH occurs precisely midway between the values governing the protonation and deprotonation of the zwitterion. Thus, .

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