The mitochondria are the power producing organelles found in every cell of every organ. Their primary job is to create Adenosine Triphosphate (ATP) and they do so in the various energy cycles that involve nutrients such as Acetyl-L-Carnitine, CoQ10 (Idebenone), NADH and some B vitamins etc.
ATP is literally the life giving chemical because every movement, thought and action we make is generated from it. Yet very little ATP can be stored in the body.
It is estimated that a 180 lb. man needs to generate an average of 80-90 lbs. of ATP daily! Under strenuous exercise the use of ATP may rise to as much as 1.1 lbs. per minute! But reserves of ATP are considered to be no more than 3-5 ounces, thus under those same strenuous exercise conditions that's approximately 8-seconds worth! Thus it becomes apparent that the mitochondria have to be very efficient and healthy, in order to produce a continuous supply of essential ATP for the necessary repair and regenerative process to occur.
Chemically speaking, under normal conditions the mitochondria are fiery furnaces and subject themselves to a lot of free radical damage (see the Free Radical Theory of Aging). They also lack most of the defenses found in other parts of the body, so as we age the mitochondria become less efficient, fewer in number and larger.
Accordingly, ATP production declines.
As organs cannot borrow energy from one another, the efficiency of each organs mitochondria are essential to that particular organs repair processes and functions. If a particular organs mitochondria fail, then so does that organ (which of course can lead to death).
Enhancement and protection of the mitochondria is an essential part of preventing and slowing aging. Enhancement can be achieved with the above mention nutrients, as well as ATP supplements themselves