The intrinsic (mitochondrial) pathway of apoptosis is initiated by which key event?

• A Cytochrome c release from mitochondria, activating Apaf-1 and the apoptosome ✓
• B Caspase-8 cleavage by FADD upon Fas ligand binding
• C Perforin-granzyme B delivery by cytotoxic T lymphocytes
• D TNF binding to TNFR1 activating the DISC complex

Explanation

The intrinsic pathway is triggered by cellular stress (DNA damage, oxidative stress, ER stress), leading to BAX/BAK pore formation in the outer mitochondrial membrane and cytochrome c release into the cytoplasm. Cytochrome c binds Apaf-1 and procaspase-9, forming the apoptosome, which activates executioner caspases-3 and -7. Options A, C, and D describe extrinsic pathway mechanisms.

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

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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