Apoptosis

Apoptosis is a cell suicide mechanism that controls cell number in tissues and eliminate cancerous cells. Death Receptors present on the surface of certain cells detect the presence of extracellular death signals and ignite the cell's intrinsic apoptosis machinery. Cytotoxic T cell with Fas ligand binds and activates the Fas receptor on target cell, which interacts with FADD (Fas-Associated Death Domain). FADD activates Caspase8, which further activates Caspase3. Activated BAX within the mitochondrial membrane leads to creation of membrane pores, resulting in release of Cytochrome-C into the cytosol. Cytochrome-C along with APAF1 and Procaspase9 form the apoptosome, which activates Caspase9, leading to activation of downstream effector Caspases. Caspase3 cleaves several substrates, thus causing apoptosis. This animation illustrates the detailed process of apoptosis by extrinsic and intrinsic pathways.