In the intrinsic (mitochondrial) pathway of apoptosis, which protein directly inhibits the release of cytochrome c by maintaining outer mitochondrial membrane integrity?

• A BCL2 ✓
• B BAX
• C Caspase-9
• D Apaf-1

Explanation

BCL2 (and BCL-XL) are anti-apoptotic proteins that reside on the outer mitochondrial membrane and maintain its integrity by binding and neutralizing pro-apoptotic proteins BAX and BAK, preventing them from oligomerizing and forming pores that release cytochrome c. When pro-apoptotic BH3-only proteins (like BIM, BAD) are upregulated, they displace BAX/BAK from BCL2, allowing cytochrome c release and apoptosome formation. Caspase-9 and Apaf-1 are downstream components of the apoptosome.

Reference: Robbins & Cotran Pathologic Basis of Disease, 10th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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