Liver cells have been found to have the most mitochondria with an estimated 1,000 to 2,000. Mitochondria can be found in all living cells.
Mitochondria do for humans what chloroplasts do for plants; they help process food to produce energy. Adenosine triphosphate production is the main function of mitochondria, and this function can be improved by aerobic exercise. Muscle and fat cells have many mitochondria because the mitochondria allow for rapid reactions and the storage of large amounts of energy.