They fly around to find their prey because "you can catch flies with honey, but you can catch more honeys being fly".
The answer is because the cell membrane is pressed against the cell wall.
I tried my best to answer.
1) Chemical to mechanical (calories -> muscle contractions)
2) mechanical to mechanical (muscle -> motion)
3) mechanical to thermal (motion -> heat from the body causes sweating)
The potential energy is stored in the body chemically (via food). That potential energy is then released when the body is put in motion.
