Two polypeptides, X and Y, have similar tertiary structures. X normally exists as a monomer while Y exists as a tetramer, Y4. What differences might be expected in the amino acid composition of X versus Y

Due to number of amino acids.

Explanation:

The main differences might be expected in the amino acid composition of X versus Y because the X polypeptide is made up of one smaller unit of amino acid while on the other hand, Y polypeptide is made up of four smaller units of amino acids. The  name of X is monomer which means composed of one amino acids while Y exists as a tetramer which means it has four amino acids. So we can conclude that the main difference between X and Y is the presence of  number of amino acids.