Which statement best describes the stabilization of the tertiary structure of a protein?

Which statement best describes the stabilization of the tertiary structure of a protein?

• A. Hydrophobic interactions and disulfide bonds
• B. Hydrogen bonds in the backbone only
• C. Peptide bonds between amino acids
• D. Ionic bonds only

Answer: (C)

The key idea is that the three-dimensional shape of a protein (its tertiary structure) is held together by interactions between the side chains of amino acids, not by the bonds that link the amino acids in the chain. Hydrophobic interactions help drive nonpolar side chains into the protein’s interior, forming a stable core, while disulfide bonds create covalent cross-links that can strongly secure parts of the chain in a particular arrangement. Together with other contacts like hydrogen bonds and ionic interactions, these side-chain interactions lock in the folded shape. Peptide bonds are responsible for linking amino acids to form the linear chain, which is the primary structure, not the folded 3D shape. Hydrogen bonds between the backbone mainly stabilize secondary structures (like alpha helices and beta sheets) rather than tertiary structure, and ionic bonds alone don’t capture the full range of forces that stabilize the fold.

The key idea is that the three-dimensional shape of a protein (its tertiary structure) is held together by interactions between the side chains of amino acids, not by the bonds that link the amino acids in the chain. Hydrophobic interactions help drive nonpolar side chains into the protein’s interior, forming a stable core, while disulfide bonds create covalent cross-links that can strongly secure parts of the chain in a particular arrangement. Together with other contacts like hydrogen bonds and ionic interactions, these side-chain interactions lock in the folded shape.

Peptide bonds are responsible for linking amino acids to form the linear chain, which is the primary structure, not the folded 3D shape. Hydrogen bonds between the backbone mainly stabilize secondary structures (like alpha helices and beta sheets) rather than tertiary structure, and ionic bonds alone don’t capture the full range of forces that stabilize the fold.