The function of mrna is while the function of rrna is a. wind the dna up, producing atp b. producing atp, wind the dna up c. a template for a protein, becoming a ribosome d. becoming a ribosome, a template for a protein

I believe the answer is A, i remember getting confused a little with this in freshman year of highschool

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.