Which statement about protein structure is INCORRECT?

AThe peptide bonds linking the residues are non-covalent interactions that break when a protein is denatured.
BThe alpha-helix is held by hydrogen bonds between backbone C=O and N-H groups.
CA disulfide bridge is a covalent link between two cysteine side chains.
DHydrophobic interactions bring non-polar side chains together in the interior of a globular protein.

Answer: A

Peptide bonds are covalent amide links and survive denaturation; breaking them needs hydrolysis by strong acid, base or enzymes. The other three statements are true.

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