Intrinsic and extrinsic pathways
The extrinsic pathway is carried out by ligating TNF related death receptors (TNF, CD95/Fas, TRAIL death receptors) on plasma membranes and their inhibitory molecules (FADD, FLIP).[Bibliography item Jeong not found.] Once these death receptors are activated, they can either inhibit or induce apoptosis.(Profyris,Jeong) The inhibitory process works by activating procaspsase-8, cleaving procaspase 3.[Bibliography item Profyris not found.] By cleaving cystolic Bid, translocating it to the mitochondrial membrane, this pathway induces apoptosis.[Bibliography item Jeong not found.,Bibliography item Profyris not found.]The intrinsic pathway of apoptosis occurs via disruptions of the cellular homeostasis.[Bibliography item Ferri not found.] Mitochondria is the prominent organelle in this pathway, and are often controlled by pro- and anti-apoptotic proteins.[Bibliography item Jeong not found.] The intrinsic pathway is initiated by apoptotic protease-activating factor-1 (Apaf-1) and procaspase-9 when they combine with cytochrome c after it is released from the cell, forming cystolic apoptosome.(Jeong) Cytochrome c is a protein stored in mitochondria.[Bibliography item Jeong not found.,Bibliography item Profyris not found.,Bibliography item Beattie not found.] This creates a trickle effect which ultimately activates caspases (-3, -6, -7); cysteine proteins designed to prevent apoptosis by activating DNA and proteins.[Bibliography item Profyris not found.,Bibliography item Sekhon not found.] These too, specifically caspase-3, releases cytochrome c from the mitochondria.[Bibliography item Jeong not found.]

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