Final answer:
The rotations between the alpha carbon and the amid nitrogen within the main chain of a polypeptide are described by amide bonds.
Step-by-step explanation:
The rotations between the alpha carbon and the amid nitrogen within the main chain of a polypeptide are described by the term amide bonds.
These bonds, also known as peptide bonds, form between the carbonyl group of one amino acid and the amine group of the adjacent amino acid.
They are responsible for holding the polypeptide chain together and giving it a primary structure.