Why is oxygen a molecule but not a compound? a) it only contains atoms of single elements b) it contains atoms from different elements c) oxygen can''t form compounds d) only ions form compounds

Oxygen is considered a molecule and not a compound because it only contains atoms of oxygen, a single element.

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.