What is the purpose of the mitochondria in cells?

Mitochondria are often referred to as the powerhouses of the cell because their primary function is to produce energy in the form of adenosine triphosphate (ATP). ATP is used by cells to perform various functions, from muscle contraction to protein synthesis. In addition to energy production, mitochondria play roles in regulating cell death (apoptosis), storing calcium, and controlling the cell cycle. Mitochondria are unique in that they have their own DNA and are thought to have originated from ancient symbiotic bacteria.