fibrous and globular The main forces which
stabilise the 2° and 3° structures of proteins are
hydrogen bonds, disulphide linkages, van der Waals
and electrostatic forces of attraction (iv) Quaternary structure of proteins: Some of the
proteins are composed of two or more polypeptide
chains referred to as sub-units The spatial
arrangement of these subunits with respect to each
other is known as quaternary structure