Final answer:
The quaternary structure describes the assembly of two or more polypeptide chains in a protein complex, like hemoglobin, and is sustained by a variety of bonds. The relevant term for describing these polypeptide arrangements is 'oligomers'.
Step-by-step explanation:
The quaternary structure of a protein refers to the arrangement of multiple polypeptide chains or subunits within a protein complex. It describes how these subunits come together to form a functioning protein. The interaction and orientation of these subunits are critical for the protein's biological function. A protein with a quaternary structure, such as hemoglobin, can be composed of different kinds of subunits (a heteromer) or identical subunits (a homomer). For instance, vertebrate hemoglobin is a heterotetramer as it consists of two α- and two β-globin chains.
The quaternary structure is held together by a variety of bonds and interactions including hydrogen bonds, ionic bonds, hydrophobic interactions, and van der Waals forces. Sometimes they may be further stabilized by disulfide bonds between cysteine residues on different polypeptide chains. In the context of the question, the correct term that refers to the arrangement of two or more polypeptides in a protein is oligomers, which can form structures such as dimers, trimers, tetramers, etc.