Final answer:
Enzymatic cleavage of APP typically produces extracellular Ab peptides of 39-43 amino acids in length, which are digested under normal conditions but accumulate and form plaques in Alzheimer's disease.
Step-by-step explanation:
In the comparison of normal vs. Alzheimer's processing, enzymatic cleavage of the amyloid precursor protein (APP) typically produces extracellular amyloid beta (Ab) peptides consisting of 39-43 amino acids. Normally, these Ab peptides are further digested to prevent accumulation. However, in Alzheimer's disease, these peptides can accumulate and form the characteristic extracellular amyloid plaques.