Activated tBid and Puma inhibit anti-apoptotic proteins (Bcl-2, Bcl-w, Bfl-1, Bcl-XL, and Mcl-1) whereas activated pro-apoptotic initiator Bim inhibits anti-apoptotic proteins (Bcl-B, Bcl-2, Bcl-w, Bfl-1, Bcl-XL, and Mcl-1). Pro-apoptotic BH3-only protein Bad inhibits anti-apoptotic proteins of (Bcl-w, Bcl-XL, and Bcl-2) while Noxa binds preferentially onto anti-apoptotic proteins (Mcl-1, and Bfl-1) and inhibit their activity in apoptosis. Activated apoptotic initiators (Bim, tBid, and Puma) initiate the activation of pro-apoptotic effectors (Bax/Bak or Bok) which leads to MOMP. Pro-apoptotic effectors are inhibited by anti-apoptotic proteins (Mcl-1, Bfl-1, Bcl-XL, Bcl-2, Bcl-w, and Bcl-B).