Lipids, otherwise know as fats, supply the most energy, 9kcal to be exact.
I am not absolutely positive, but I would have to say bananas.
If you mean the most energy per unit weight of the fuel, this is uranium at present. In the future if nuclear fusion can be made to work, this will provide even more per unit weight (by unit weight I...
The mitochondria produce ATP, the main energy source for cells.
fats