Proteins are not held together by covalent bonds. Instead, they are held together by peptide bonds.

Here's the breakdown:

* Covalent bonds involve the sharing of electrons between atoms. This is a very strong type of bond and is typically found within molecules.

* Peptide bonds are a specific type of covalent bond that forms between the amino group (-NH2) of one amino acid and the carboxyl group (-COOH) of another amino acid. These bonds are what link amino acids together to form polypeptide chains, which are the building blocks of proteins.

While proteins themselves are not held together by covalent bonds, there are disulfide bridges that can form between cysteine amino acids within a protein. These bridges are covalent bonds and help to stabilize the protein's structure.

So, while covalent bonds are important in forming the individual peptide bonds that link amino acids in proteins, they are not the primary force holding the protein together.