Final answer:
The protein quality control model involves chaperone-assisted folding and refolding of proteins or their ubiquitin-mediated degradation by the proteasome when they misfold.
Step-by-step explanation:
The statement in question refers to a protein quality control model, which is a crucial biological process safeguarding the integrity of proteins within the cell. Proteins are synthesized and folded into specific secondary, tertiary, and quaternary structures to perform their intended functions. However, if a protein misfolds, it can become non-functional and potentially harmful to the cell. Chaperone proteins assist in the correct folding and refolding of these proteins. When proteins are irreversibly misfolded and cannot be refolded by chaperones, they are targeted for destruction by a mechanism involving a molecule called ubiquitin, which tags the defective proteins for degradation by the proteasome.