The Yin and Yang of Cell Death Control

Mitochondria are primarily responsible for producing ATP via oxidative phosphorylation in the inner mitochondrial membrane. Because of the high energy demand of the heart, mitochondria comprise at least 30% of the myocyte volume. Mitochondria also play central roles in both necrosis and apoptosis and can quickly change from a source of energy for sustaining contraction to an organelle that promotes cell death. In response to changes in the environment, ATP synthesis is disrupted, and mitochondria become producers of excessive reactive oxygen species (ROS) and release proteins that participate in cell death pathways. Interestingly, cells have developed a defense mechanism against aberrant mitochondria, which can cause harm to the cell. This mechanism involves selective