Structure of amino acids

All proteins are formed of 20 amino acids.They are mainly formed of α amino acids (except proline).They have COOH and NH3 on same carbon atom. In physiological conditions both the groups are are completely ionised so an amino acid can act both as acid and base (amphoteric)

1. STRUCTURE OF AMINO ACIDS FEBA SHAJI I M Sc BIOCHEMISTRY

2. THE AMINO ACIDS OF PROTEINS All proteins are formed of 20 amino acids They are mainly formed of α amino acids (except proline ) They have COOH and NH 3 on same carbon atom In physiological conditions both the groups are are completely ionised so an amino acid can act both as acid and base (amphoteric)

3. Molecules that bear charged groups are of opposite polarity are known as zwitter ion It has been established using spectroscopic and X-ray crystal structure They have properties of ionic compound(high MP) Amino acid are more soluble in polar compounds like water They are in L isomeric form

4. Amino acids are named based on two conventions Three letter code is transparent, the name has first three letter of amino acid One letter code was devised by Margaret Oakeley Dayhoff Except glycine all amino acids has a chiral centre .

5. Based on the R groups present amino acids can be classified as under:- Non polar , aliphatic R group Polar , uncharged R group Aromatic R group Positively charged R group Negatively charged R group

6. REFERENCES Principles of Biochemistry – Lehninger 5 th edition – David L Nelson, Michael M Cox Biochemistry - 7 th edition -Campbell , Farrell Biochemistry – 3 rd edition - Donald Voet and Judith Voet