In apoptosis, permeabilization of the membrane occurs in

Mitochondria contain several proteins that are capable of inducing apoptosis; these proteins include cytochrome c and other proteins that neutralize endogenous inhibitors ofapoptosis. When cells are deprived of growth factors and other survival signals, or are exposed to agents that damage DNA, or accumulate unacceptable amounts of misfolded proteins, a number of sensors are activated. These sensors are members of the Bcl-2 family called "BH3 proteins" (because they contain only the third of multiple conserved domains of the Bcl-2 family). They, in turn, activate two pro-apoptotic members of the family called Bax and Bak, which dimerize, inse into the mitochondrial membrane, and form channels through which cytochrome c and other mitochondrial proteins escape into the cytosol.( Robbins Basic Pathology, 9th edition, page 18 )