The main roles of mitochondria are to produce the energy currency of the cell, ATP, and to regulate cellular metabolism. Mitochondria play a central role in many metabolic tasks, such as:

· Regulation of the membrane potential

· Apoptosis-programmed cell death

· Calcium signaling (including calcium-evoked apoptosis)

· Regulation of cellular metabolism

· Certain heme synthesis reactions

· Steroid synthesis.

Some mitochondrial functions occur only in certain types of cells. For example, mitochondria in liver cells have enzymes that enable them to detoxify ammonia.