amino acids

Biochemistry

Amino acids and proteins

Prof. Dr.
Abdulhussien M. Aljebory
Babylon University
College of Pharmacy
Amino Acids are the building units of proteins. Proteins are polymers of amino acids linked together by what is called “ Peptide bond” .
There are about 300 amino acids occur in nature. Only 20 of them occur in proteins.
Structure of amino acids:
Each amino acid has 4 different groups attached to ?- carbon ( which is C-atom next to COOH). These 4 groups are : amino group, COOH gp,
Hydrogen atom and side
Chain (R)
Same general structure
Called alpha amino acids
L- isomer is physiologically active
Side chain or R group determines other properties
Acid-base properties
At physiological PH (7.4), -COOH gp is dissociated forming a negatively charged carboxylate ion (COO-) and amino gp is protonated forming positively charged ion (NH3+) forming Zwitter ion

Classification of amino acids
I- Chemical classification: According to number of COOH and NH2 groups i.e. according to net charge on amino acid.
A- Monobasic, monocarboxylic amino acids i.e. neutral or uncharged: