This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: General pathology, Subject name: Pathology
In apoptosis, cytochrome C acts through 
Select and explain. 
A. Apaf 1, B. Bc1-2, C. FADD, D. TNF
A: Apaf 1
Answer: A: Apaf 1 
Explanation: Cytochrome c leaks into the cytosol, where it binds to APAF-1 andactivates caspase-9. Like caspase-8 of the extrinsic pathway, caspase-9 can cleave and activate the executioner caspases. The integrity of the mitochondrial outer membrane is regulated by pro-apoptotic and anti-apoptotic members of the BCL2 family of proteins( Robbins Basic Pathology, 9 th edition)