Preteins vary widely in structure, whereas nucleic acids have rather uniform structures. How do you account for this major difference?

As proteins vary widely in structures than that of nucleic acid there will be greater structural and functional diversity of proteins than nucleic acid.

Explanation:

Proteins are the macromolecules which have more structural diversity than any other macromolecules such as carbohydrate, lipid, nucleic acid.

The are 4 types of protein structure primary structure, secondary structure, tertiary structure and Quaternary structure. Due the existence of many types of structure various protein exhibit various functions.

On the other hand nucleic acid such as DNA has widely accepted secondary structure discovered by watson and crick. As a result there is no such structural diversity exist in nucleic acid.