destruction of mitochondrial transmembrane potential, which is widely regarded as one of the earliest events in the process of cell apoptosis.
Mitochondria are organelles within eukaryotic cells that produce adenosine triphosphate (ATP), the main energy molecule used by the cell. For this reason, the mitochondrion is sometimes referred to as “the powerhouse of the cell”. 
Mitochondria produce ATP through process of cellular respiration—specifically, aerobic respiration, which requires oxygen. The citric acid cycle, or Krebs cycle, takes place in the mitochondria.
The mitochondrial membrane potential is widely used in assessing mitochondrial function as it relates to the mitochondrial capacity of ATP generation by oxidative phosphorylation. The mitochondrial membrane potential is a reliable indicator of mitochondrial health.
In cancer cells, ΔΨm is often decreased, which can lead to changes in cellular metabolism, increased glycolysis, increased reactive oxygen species (ROS) production, and altered cell death pathways.