What is the difference between an amyloid and a prion? is alzheimer's suspected to be from a prion?

Prions are amyloids: But not all amyloids are prions. Alzheimer's disease behaves like a prion in its spread through the brain but not from person to person.

No: Prion causes different disease that also causes dementia. Prion is a different protein than amyloid. It is infectious while amyloid is not.

Great question, but: Prions are v small protein-like structures that have been found to be essential to normal memory-indeed that underly most of biology (see susan whitehead prion research). Amazingly, they replicate without nucleic acids. They are also implicated in other neurodegenerative disease. That they might cause ad excited many researchers, yet little evidence for this has been found.