This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Misc., Subject name: Pathology
Bcl-2 is 
Select and explain. 
A. Pro-apoptotic, B. Anti-apoptotic, C. Protein synthesis, D. Gene amplification
B: Anti-apoptotic
Answer: B: Anti-apoptotic 
Explanation: (B) Anti-apoptotic > The two main anti-apoptotic proteins are Bcl-2 and Bcl-x.> These anti-apoptotic proteins normally reside in mitochondrial membranes and the cytoplasm.> When cells are deprived of survival signals or subjected to stress, Bcl-2 and/or Bcl-x are lost from the mitochondrial membrane and are replaced by pro-apoptotic members of the family, such as Bak, Bax, and Bim. When Bcl-2/Bcl-x levels decrease, the permetability of the mitochondrial membrane increases, and several proteins that can activate the caspase cascade leak out.