If a substance disrupts the primary structure of a polypeptide, does it also disrupt the secondary, tertiary, and quaternary structures of the polypeptide? In general,"disruption" of the primary structure really represent the destruction of the protein, which is a polymer. If the protein is hydrolyzed back to its constituent amino acids, then there is no more polymer, never mind one that could fold. That said, we could consider less severe disruptions of primary structure than cleavage of all the peptide bonds. Cleavage of many peptide bonds would also destabilize the structure, with small peptides not providing the cooperative effects necessary to keep the protein folded in the face of thermal agitation. However, if we go to the extreme low end of disruption of primary structure, the cleavage of just a single peptide bond, then there may be enough stability and cooperation among all the weak binds to allow a polypeptide to stay together in a proper tertiary structure (which now might be better considered a quaternary structure, since the cleavage would result in two polypeptide chains). This was the case for the problem in set 2 for ribonuclease. One would think a protein could better tolerate such a minimal cleavage event if there were disulfide bonds helping to stabilize the tertiary structure.