6. Sketch a titration curve for aspartic acid, and indicate the pKa values of all titratable groups. Also indicate the pH range in which the conjugate acid–base pair +1 Asp and 0 Asp will act

Answer 1

I cannot sketch anything on this site, but here is the explanation.

Aspartic acid is a dicarboxylic amino acid. Thus it has THREE titratable groups, each with its own pKa.

The values I found are:

pKa1 = 1.88 for the first carboxyl group

pKa2 = 3.6 for the 2nd carboxyl group

pKa3 = 9.6 for the amino group

If you could draw the titration curve, pKa1 would be at the first plateau, pKa 2 at the 2nd plateau and pKa3 at the third and final plateau.

For the conjugate base to have a net +1 charge, the pH would be below pKa1.

For the conjugate base to have a net charge of 0, the pH would be at the pI. which will be 1/2 way between pKa1 and pKa2.