At the end of cellular respiration, energy is stored in the bonds of blank molecules.

ADP (adenosine diphosate) 
Then comes 
ATP (adenosine triphosphate)
(Confidently Correct)
Because:
ADP is the starting molecule for the reaction which occurs at the start as it moves down the chains such as the kreb cycle, the nutrients is then packed into and converted into ATP for Storage and later use for the cells required energy.

At the end of cellular respiration, energy is stored in the bonds of ATP molecules.

In short, you answer would be : ATP.

Hope this helps !

Photon

Gravitational force i believe