First we have to identify what substance produces the most energy that an organism (human) can utilize. Adenosine triphosphate (ATP) is the major energy-producing substance that any organism can use for any work. It can produce energy when it reacts chemically and lose one of the phosphate and forms ADP (adenosine diphosphate). Which organelle then is responsible for the production of ATP?
Mitochondria, a membrane bound orgnelle is the ATP producing unit of the cell. If Mitochondria is malfunctioning, the production of energy will be suppressed. Even though you have a lot of external energy sources such as foods, vitamis and minerals, you cannot utilize them efficiently if the mitochondria is not functioning very well. Even the breaking down of food that a body intakes needs a large amount of ATP for the digestion to proceed.
The answer is mitochondria.
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