Amyloid fibrils are associated with many fatal degenerative diseases of humans and livestock. Livestock diseases such as scrapie in sheep and bovine spongiform encephalitis (BSE, or mad cow disease) have major negative impacts on agriculture. Human diseases characterized by amyloid fibrils include Alzheimer's disease and Creutzfeldt-Jakob disease.

Choose the true statements about amyloid fibrils.

a. Amyloid fibrils have a high amount of β-sheet structure.
b. Proteins that convert to an amyloid structure form soluble fibrils.
c. Because most newly synthesized proteins fold correctly, the accumulation of misfolded proteins (or fragments) tends to occur slowly, thus explaining the slow onset of disease.
d. An amyloid fibril is stabilized by hydrogen bonds between small hydrophilic residues.
e. Proteins that form amyloid fibrils are normally soluble.

c. Because most newly synthesized proteins fold correctly, the accumulation of misfolded proteins (or fragments) tends to occur slowly, thus explaining the slow onset of disease.

e. Proteins that form amyloid fibrils are normally soluble.

Explanation:

Amyloids can be defined as fibrillar protein aggregates composed of a β-sheet secondary structure. In general, the amyloid fibrils are composed by soluble proteins that are assembled to form insoluble resistant to degradation fibers. In humans, defective amyloid proteins produced by misfolding are known to produce diseases (amyloidosis) capable of altering the function of tissues and organs. Systemic forms of amyloidosis are common in neurodegenerative disorders.