Which type of cell death is characterised by mitochondrial outer membrane permeabilisation (MOMP) releasing cytochrome c, activating caspase-9 via the apoptosome?

• A Intrinsic apoptosis (mitochondrial pathway) ✓
• B Extrinsic apoptosis (death receptor pathway)
• C Pyroptosis (caspase-1/11 mediated)
• D Necroptosis (RIPK3/MLKL mediated)

Explanation

The intrinsic (mitochondrial) apoptosis pathway is initiated by cellular stress (DNA damage, growth factor withdrawal) leading to BAX/BAK oligomerisation and MOMP. Cytochrome c released into the cytosol forms the apoptosome with APAF-1 and procaspase-9, activating caspase-9, which then cleaves and activates executioner caspases-3/7. The extrinsic pathway uses death receptors (Fas/TRAIL-R) to activate caspase-8. Pyroptosis uses inflammasome-activated caspase-1 or -11 to cleave gasdermin D. Necroptosis is caspase-independent and requires RIPK3-mediated MLKL phosphorylation.

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

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.