Final answer:
Amyloid protein structures consist of stacked ß sheets, not helical protein fibers, and they do not always cause neurodegenerative diseases. They can aggregate into plaques, which are associated with diseases such as Alzheimer's, but not all amyloids lead to disease conditions.
Step-by-step explanation:
The correct answer to the question of what is true about amyloid protein structures is that they consist of stacked ß sheets. In the context of diseases such as Alzheimer's and other neurodegenerative diseases, normal soluble proteins sometimes misfold from their natural α helix configuration into ß-pleated sheets. When proteins misfold in this way, they can aggregate and form amyloid plaques, which are insoluble fibrils, and these aggregations have been associated with various diseases.
The accumulation of these fibrils is not necessarily the result of functional loss of the proteins, but rather, the altered proteins accumulate and can become toxic. This kind of disease is known as a proteopathy, which includes but is not limited to Alzheimer's disease. Moreover, not all amyloid structures are associated with disease, as their presence doesn't always lead to neurodegenerative conditions. While some amyloids are implicated in diseases, others are functional and play normal biological roles.
It is important to recognize that amyloid protein structures being made up of helical protein fibers is incorrect, and that they are not always the cause of neurodegenerative diseases, nor are they categorically weak and brittle. Understanding the nature of amyloid protein structures and their role in disease can suggest new therapeutic possibilities to manage these conditions.