In the intrinsic (mitochondrial) pathway of apoptosis, cytochrome c released from mitochondria binds to which cytoplasmic adaptor protein to form the apoptosome?

• A FADD (Fas-associated death domain)
• B TRADD (TNFR-associated death domain)
• C RIP1 (receptor-interacting protein kinase 1)
• D Apaf-1 (apoptotic protease activating factor-1) ✓

Explanation

In the intrinsic pathway, BAX/BAK form pores in the mitochondrial outer membrane, releasing cytochrome c into the cytosol. Cytochrome c binds to Apaf-1, inducing its oligomerization into the heptameric apoptosome, which recruits and activates procaspase-9. Active caspase-9 then cleaves downstream effector caspases (caspase-3, -6, -7) to execute apoptosis. FADD and TRADD are adaptor proteins in the extrinsic (death-receptor) pathway; RIP1 mediates necroptosis.

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

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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