In: Chemistry
Does all Nonpolar amino acids have the same titration curve?
Yes, your assumption is right. If the amino acid has no ionizable groups on the side chain then there will be no protonation or, deprotonation when we'll monitor by varying pH. So, the titration curve will be only a result of the protonation and deprotonation on -NH2 and -COOH site of the amino acid. So, the titration curves of such amino acids will be of similar nature, consisted of two sigmoidal change (equivalence points), but may not be exactly a photocopy of each other, just because the polar or, non-polar character of side chain influences the pKa values of the ionizable groups.
If an amino acid has ionizable group at the side chain, then it will provide an extra equivalence point when we'll run a titration experiment. Where the extra sigmoidal rise will come, that totally depends upon the ionizable group, whether it is basic or, acidic. But the fact is, the titration curve will be consisted of 3 sigmoidal rises corresponding to three equivalence points.