Why are mitochondria important in the decision for a cell to die?

Mitochondria are central to the decision-making process of apoptosis, or programmed cell death, serving as the site where a cell's mortality is constantly reviewed.1

In mammals, this regulation is controlled by the BCL-2 family of proteins, which function on the mitochondrial membranes. This family consists of three contesting factions:1
* BH-3-only proteins: These act as sensors that monitor cellular processes for dysfunction and serve as activators or sensitizers of apoptosis.1
* Pro-apoptotic proteins (Bax and Bak): These initiate the death process.1
* Anti-apoptotic proteins (such as BCL-2 and BCL-XL): These work to prevent cell death.1

The balance between these proteins on the mitochondrial membrane determines whether a cell will undergo apoptosis. Once the death decision is confirmed, the cell proceeds to the execution phase, involving caspase proteolytic enzymes that dismantle the cell's internal structures. Because mitochondria are essential to this regulatory mechanism, mitochondrial dysfunction that inhibits apoptosis can contribute to the development of cancer, as abnormal cells fail to self-destruct.12