In the intrinsic (mitochondrial) pathway of apoptosis, cytochrome c release from mitochondria is triggered by pro-apoptotic BAX and BAK. The anti-apoptotic protein that normally prevents cytochrome c release by binding BAX is:

• A BCL-2 ✓
• B Caspase-9
• C APAF-1
• D Smac/DIABLO

Explanation

BCL-2 is the prototype anti-apoptotic protein; it resides on the outer mitochondrial membrane and inhibits BAX/BAK by heterodimerization, preventing mitochondrial outer membrane permeabilization (MOMP) and cytochrome c release. Apoptotic signals shift the balance toward pro-apoptotic BH3-only proteins (BIM, BID, PUMA) that neutralize BCL-2. Caspase-9 is activated downstream after cytochrome c release; APAF-1 forms the apoptosome with cytochrome c; Smac/DIABLO inhibits IAPs to amplify caspase activation.

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

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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