Final answer:
PrPSc, the infectious form of the prion protein, differs from the normal PrPC in structure by having more β-pleated sheets, being protease resistant, and being able to convert normal PrPC into more PrPSc, leading to disease.
Step-by-step explanation:
Prion protein (PrP) exists in two forms: the normal cellular form, PrPC, and the infectious form, PrPSc. PrPSc is different from PrPC in its structure; it has a high content of β-pleated sheets compared to the α-helix content predominant in PrPC. This structural difference makes PrPSc resistant to protease enzymes which normally degrade proteins. Additionally, PrPSc aggregates and forms amyloid plaques which are associated with neurodegeneration. Once PrPSc is introduced into the body, it can bind to normal PrPC and convert it into more PrPSc, leading to a chain reaction and disease progression.