Final answer:
The true statement is that disulfide bonds stabilize but do not change a protein's final conformation, with the bonds forming through the oxidation of cysteine residues to create cystine, leading to stabilization of the protein structure.
Step-by-step explanation:
The statement that is true among the options provided is:
C) Disulfide bonds stabilize but do not change a protein's final conformation. Disulfide bonds are covalent bonds that form when the thiol groups of two cysteine residues oxidize and link together to form cystine. This process occurs between sulfur atoms in the cysteine amino acid residues of a protein. These bonds are essential for the stabilization of a protein’s tertiary structure, providing rigidity and resistance to denaturation under certain conditions. Disulfide bridges are most commonly found within proteins that are secreted or located outside the cytosol, such as in the extracellular space or within the endoplasmic reticulum, where the oxidizing environment facilitates the formation of these bonds.
Reductive agents, like mercaptoethanol, can break disulfide bonds, but they do so via reduction, not oxidation as stated in option D. Therefore, agents such as mercaptoethanol break disulfide bonds through reduction, not oxidation.