BIOMOLECULES AND ENZYMES

Detailed explanation-1: -The quaternary structure of a protein is the association of several protein chains or subunits into a closely packed arrangement. Each of the subunits has its own primary, secondary, and tertiary structure. The subunits are held together by hydrogen bonds and van der Waals forces between nonpolar side chains.

Detailed explanation-2: -Some proteins form assemblies (units) with other molecules – this is called the quaternary structure (Figure 14). Two examples are: haemoglobin which is an assembly of four globular proteins and the actin microfilament, composed of many thousands of actin molecules.

Detailed explanation-3: -The two most common quaternary structures of multisubunit proteins are -helices in globular proteins and -sheets in fibrous proteins. The functional properties of multi-subunit proteins depends on the quaternary structure.

Detailed explanation-4: -Proteins with a quaternary structure can be classified into homomultimeric, that is, proteins that have identical subunits, and heteromultimeric, which are proteins with different types of subunits.