The correct folding of proteins is necessary to maintain healthy cells and tissues. Unfolded proteins are responsible for such neurodegenerative disorders as Alzheimer's disease, Huntington's disease, and Creutzfeldt-Jakob disease (the specific faulty protein is different for each disease). What is the ultimate fate of these disease-causing, unfolded proteins?
(a) They are degraded.
(b) They bind a different target protein.
(c) They form structured filaments.
(d) They form protein aggregates.
Answer: D