AS.020.305 Midterm: cell bio final study sheet (dragged) 12
Document Summary
Apoptotic*cells*are*biochemically*recognizable: during apoptosis, an endonuclease cleaves the chromosomal dna into fragments of distinctive sizes. Because the cleavages occur in the linker regions between nucleosomes, the fragments separate into a characteristic ladder pattern when analyzed by gel electrophoresis: an especially important change occurs in the plasma membrane of apoptotic cells. Apoptosis*depends*on*an*intracellular*proteolytic*cascade*that*is*mediated*by*caspases*: the intracellular machinery responsible for apoptosis is similar in all animal cells. It depends on a family of proteases that have a cysteine at their active site and cleave their target proteins at specific aspartic acids. They are therefore called caspases (c for cysteine and asp for aspartic acid). Once incorporated into such a complex, the initiator procaspases are brought into close proximity, which is sufficient to activate them; they then cleave each other to make the process irreversible. Cellasurface*receptors*activate*the*extrinsic*pathway*of*apoptosis: extracellular signal proteins binding to cell-surface death receptors trigger the extrinsic pathway of apoptosis.
