BIOMOLECULES AND ENZYMES

Detailed explanation-1: -However, some proteins are made up of multiple polypeptide chains, also known as subunits. When these subunits come together, they give the protein its quaternary structure.

Detailed explanation-2: -Quaternary structure exists in proteins consisting of two or more identical or different polypeptide chains (subunits). These proteins are called oligomers because they have two or more subunits. The quaternary structure describes the manner in which subunits are arranged in the native protein.

Detailed explanation-3: -Quaternary Structure of Proteins Many proteins are formed from more than one polypeptide chain. The quaternary structure describes the way in which the different subunits are packed together to form the overall structure of the protein. For example, the human hemoglobin molecule shown below is made of four subunits.

Detailed explanation-4: -To be considered to have quaternary structure, a protein must have two or more peptide chains forming subunits.

Detailed explanation-5: -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.