AP BIOLOGY

Detailed explanation-1: -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.

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.

Detailed explanation-3: -Finally, the quaternary structure of a protein refers to those macromolecules with multiple polypeptide chains or subunits.

Detailed explanation-4: -The quaternary structure describes the arrangements of subunits in a protein that contains more than one subunit. Four major types of attractive interactions determine the shape and stability of the folded protein: ionic bonding, hydrogen bonding, disulfide linkages, and dispersion forces.

Detailed explanation-5: -Quaternary protein structure is held together by hydrophobic interactions, and disulfide bridges.