How is decaying organic matter important to the carbon cycle? a. It produces fossil fuels that store energy b. It fixes carbon from the atmosphere c. It returns carbon to carbon dioxide gas d. It transfers usable carbon from plants to animals.

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.