The plaques:
Plaques consist of a potein called beta amyloid, or A-beta. These proteins are actually split from a larger protein molecule know as APP. These proteins are present in normal brains, but no one knows their exact function. The problem with it in a brain with Alzheimer's is that there is a much higher concentration. The A-beta protein begins to accumulate causing certain enzymes and other molecules to be overwhelmed. Those molecules have the job to clear the A-beta protein a way, but are unable to because of the high concentration. when unable to clear the A-beta away this aggetates and begin to stick together causing the amyloid plaques.
The Tangles:
Tangles are made out of a protein called tau, and also occurs in normal nerve cells. However, in Alzheimer's disease the tangles become altered, and they begin to pile up in large amounts similar to what you would imagine to be thread-like tangels. The tau protein's role initially is nerve sprouting which acts as a form of self-repair. It also has the job of maintaining a type of railway track system of nerve cells. In Alzheimer's these tangles begin to accumulate, and eventually choke cells. The first casualties are nerve endings, which are consequently the earliest signs of Alzheimer's.
