Mitochondria

Mitochondria were intracellular structures in biological lifeforms that play a key role in metabolism. They were believed to have originated from a symbiotic relationship between an ancient unicellular organism and another that had entered it. 

During a scan of Aldean DNA, Doctor Beverly Crusher was able to confirm that mitochondrial deficiencies were not responsible for the Aldeans sterility. 

Mitochondrial structure is recorded by the transporter, and is often useful for identifying remains following a transporter accident. In 2367, Doctor Crusher compared the mitochondrial structure from the remains of Vulcan Ambassador T'Pel to that of her last transport. The discrepancies between the remains and the transporter pattern led Crusher and Lieutenant Commander Data to deduce that the remains had been replicated, indicating Romulan treachery. 

Elias Giger claimed Doctor Bathkin of Andros III believed he could keep cells energized by "teaching them new mitochondrial tricks". 

In 2372, Julian Bashir studied plants on Bopak III that had adenosine triphosphate forming enzymes in their mitochondria, while trying to see what had "cured" Goran'Agar of his addiction to the Dominion's ketracel-white. 

The Doctor gave Naomi Wildman a lesson on cellular biology in early 2375. Mitochondria were part of the topic; Naomi likened them to "the warp core of the cell." 

Multiphasic prions initially attached themselves to the mitochondrial walls before migrating to the cell membranes.