The amino acid serine can ionize as follows:

with pKa1 = 2.2 and pKa2 = 9.2

What is the isoelectric point (pI) of the zwitterion?

 

 

There are now 22 known genetically encoded amino acids. Althoughanother surprising and unusual

source, amino acids have even been discovered in meteorites.Suppose you are studying one of the new

amino acids and find it has the following pKa values:

pKa1 value of 2.42 with a pKa2 value of9.61.

(A) What is the value of the fraction of species for H2A+ at apH = 3.00?

(B) Of the following statements about amino acids, which one istrue? (circle choice)

(i) The fraction of species for an amino acid in the form ofLwill decrease as pH rises

(ii) The isoelectric point for an amino acid is found when a HL= a L-

(iii) When pH = pKa2; the zwitterion is the principalspecies

(iv) At the isoelectric point, the a for HL = 1.

(v) The fraction of species of H2A+ will increase as pHrises.