Dissociation Constant

Amino acids exit aqueous solutions as dipolar ions (zwitterions), and glutamic acid may be represented as follows (16). Following Bronsted, an acid may be defined as a substance capable of combining with a proton. When an amino acid is titrated with HCl and NaOH, a curve exhibiting two points of inflection is obtained. Thus amino acid can react either as an acid or as a base, that is, as an ampholyte.

The dissociation constants for glutamic acid are pK1 2.19 (COOH), pK2 4.25 (COOH), and pK3 9.67 (NH3+). (It is customary to designate the pK values of amino acids in order of decreasing acidity.) The isoelectric point (pI) of glutamic acid is the pH 3.2 calculated from the relation pI = pK1 3 pK2/2, at which there is no net charge on the amino acid molecule. At this pH, no migration will occur in an electric field.

Brew Your Own Beer

Brew Your Own Beer

Discover How To Become Your Own Brew Master, With Brew Your Own Beer. It takes more than a recipe to make a great beer. Just using the right ingredients doesn't mean your beer will taste like it was meant to. Most of the time it’s the way a beer is made and served that makes it either an exceptional beer or one that gets dumped into the nearest flower pot.

Get My Free Ebook

Post a comment