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.

How does land development destroy ecosystems? it increases human carrying capacity too rapidly. it converts them into residential or agricultural areas. it forces humans to import non-native plants and animals. it expands the natural range of native wildlife species.

The dna in a cell’s nucleus encodes proteins that are eventually targeted to every membrane and compartment in the cell, as well as proteins that are targeted for secretion from the cell. for example, consider these two proteins: phosphofructokinase (pfk) is an enzyme that functions in the cytoplasm during glycolysis. insulin, a protein that regulates blood sugar levels, is secreted from specialized pancreatic cells. assume that you can track the cellular locations of these two proteins from the time that translation is complete until the proteins reach their final destinations.for each protein, identify its targeting pathway: the sequence of cellular locations in which the protein is found from when translation is complete until it reaches its final (functional) destination. (note that if an organelle is listed in a pathway, the location implied is inside the organelle, not in the membrane that surrounds the organelle.)

Which of the following statements about archaea and bacteria is true? a. neither is single-celled. b. they both have nuclear membranes. c. neither reproduces by binary fission. d. they both lack a nuclear membrane.