Denaturation breaks the covalent bonds that hold the protein in its three-dimensional shape. Without the proper shape, the protein cannot function.

Different amino acids are substituted into the sequence, so the protein's properties change.

Denaturation breaks the intramolecular bonds, such as hydrogen bonds and van der Waals interactions, that hold the protein in its three-dimensional shape. Without the proper shape, the protein cannot function.

Denaturation destroys the primary structure of the protein, and the protein breaks down to monomers.

The protein's pH changes, and the change causes the protein to lose its functionality.