2007-01-08 07:32:53 · 3 answers · asked by Anonymous in Science & Mathematics ➔ Chemistry
amino acids are zwitterionic, they have (at least) two ionisable groups the amino NH3+ and the carboxylic COO- group. The two pKa s show at what pH each of those groups change ionisation state.
Some amino acids have a third pKa as they have an ionisable R group attached to the amino acid backbone, e.g. Histidine.
2007-01-08 07:55:02 · answer #1 · answered by Ellie 4 · 3⤊ 0⤋
Amino acids have at least two different ionizable groups. Every AA has a carboxyl group which will have a pKa around 2 and an amino group which has a pKa around 9-10. Some amino acids have a third ionizable group on their side chains. These then, would have 3 different pKa's.
2007-01-08 07:41:15 · answer #2 · answered by hcbiochem 7 · 2⤊ 0⤋
pKa1 for -COOH
pKa2 for -NH3(+)
2007-01-08 07:41:52 · answer #3 · answered by Norman Arthrun 1 · 1⤊ 0⤋