1 Basic four chain structure A four poly peptide chains (b) two identical light chains two identical heavy chains, held by disulfide bonds binding Hinge * Y-shape structure symmetrIc. Biological ctIvity 12 一NH2 terminal, cHe CHO CooH term inal *** variable constant reglons **** domains* A four polypeptide chains: two identical light chains two identical heavy chains , held by disulfide bonds. ** Y-shape structure, symmetric. *** –NH2 terminal, - COOH terminal. **** variable & constant regions. ***** domains 1 Basic four chain structure