About 70% of our planet is covered by oceans. compared to the depth of the solid portion of earth, the water on earth forms what?

Actually about 71% of our planet is covered in water. The water on earth forms oceans, lakes, rivers, soil moisture, glaciers, icecaps and water vapor In the atmosphere. Water also makes up a high percentage of all organisms.

Mitochondria produce atp, a high energy compound. atp is used for all sorts of enzyme-mediated reactions, such as making proteins/nucleotides/etc, certain compounds cross the cell membrane, muscles move, etc.  without this source of energy, a cell will die. it will not be able to repair itself, defend against pathogens, etc.