Final answer:
The true statement about disulfide bonds is that they stabilize a protein's final conformation without changing it, and are formed between cysteine residues through oxidation, while agents like mercaptoethanol break these bonds through reduction.
Step-by-step explanation:
The correct statement regarding disulfide bonds in proteins is (c) Disulfide bonds stabilize but do not change a protein's final conformation. Disulfide bonds are covalent bonds formed between the sulfur atoms of two cysteine residues within a protein. When the sulfhydryl (SH) groups of two cysteine amino acids come in proximity as the protein folds, they can be oxidized, forming a disulfide bond (-S-S-) which helps to stabilize the protein's tertiary structure. Such a bond does not change the final conformation of the protein but provides stability to the already folded protein. While it is true that reducing agents like mercaptoethanol can break these disulfide bonds, they do so through reduction, not oxidation.