Final answer:
Denaturation usually does not affect the protein's primary structure because it is held together by strong covalent bonds that are not broken by conditions that typically cause denaturation.
Step-by-step explanation:
Denaturation usually does not affect the primary structure of proteins because the primary structure is held together by covalent bonds. These bonds, specifically peptide bonds, are much more robust compared to the non-covalent interactions—such as hydrogen bonds, ionic bonds, and hydrophobic interactions—that stabilize the secondary, tertiary, and quaternary structures. Therefore, denaturation generally alters these higher-level structures without breaking the strong covalent linkages that form the protein's primary sequence.