ATP is the most prominant energy carrier molecule. It is used to allow unfavourable reactions to occur. Like Muscle movement (they cannot move without energy). The energy in ATP is stored in its high energy phosphodiester bonds (it has 2 of them) - Therefore, there are 3 states, ATP, ADP, AMP.

ATP is limited to a cell, it cannot be transported between the cells, other mediums are used for that transportation, such as glucose (sugar). Energy storage in the body in order of effectiveness are, ATP, Glucose, Glycogen, Fat (there are others but they are minor e.g. creatine).

The energy does "go out" of our body, primarily as heat.

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