Bcl-2 family proteins regulate apoptosis at the mitochondrial level. In the intrinsic pathway, cytochrome c release from the mitochondrial intermembrane space is facilitated by:

• A Caspase-8 directly cleaving the outer mitochondrial membrane
• B BAX/BAK oligomerisation forming pores in the outer mitochondrial membrane ✓
• C Increased mitochondrial membrane potential, causing osmotic swelling
• D p53 directly inserting into the inner mitochondrial membrane

Explanation

In the intrinsic apoptotic pathway, BH3-only proteins (e.g., BIM, PUMA) neutralise pro-survival Bcl-2/Bcl-XL, unleashing BAX and BAK. BAX/BAK oligomerise in the outer mitochondrial membrane, forming proteolipid pores (mitochondrial outer membrane permeabilisation, MOMP) through which cytochrome c escapes. Released cytochrome c binds APAF-1 and procaspase-9 to form the apoptosome, activating executioner caspases. Caspase-8 operates in the extrinsic pathway.

Reference: Harper's Illustrated Biochemistry, 32nd ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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