Amphoteric Properties of Proteins

Group 3Agus Arianto (F02111013)

Atikah (F02111045)Desy Indra Wahyuni (F02111033)

Nur Desi Yani (F02111007)

Acid-Base Properties of Amino Acids

All amino acids contain at least two ionizable groups the α-amino group and the α-carboxylic group, some contain an additional acidic or basic group in their side chain,which are responsible for the amino acids, acid-base behaviour. As a result of their ionizability the following equilibrium reaction can be written:R-COOH R-COO- + H+

R-NH2 R-NH3 +

Since these reactions are reversible this indicates that they can act as acids or as bases.

Amphoteric Properties of Amino Acids

Amino acids due to the presence of their ionizable α-amino and α-carboxylic group can act sometimes as acids and sometimes as bases depending on the pH of their media.

Zwitterions

• In chemistry, a zwitterion (formerly called a dipolar ion) is a neutral molecule with a positive and a negative electrical charge.

• Unlike simple amphoteric compounds that might only form either a cationic or anionic species depending on external conditions, a zwitterion simultaneously has both ionic states in the same molecule.

http://en.wikipedia.org/wiki/File:Amino_Acid_Zwitterion_Structural_Formulae_V.1.svg