Aeukaryotic cell does not have membrane-bound organelles. is usually smaller than a prokaryotic cell. has membrane-bound organelles. has a cell wall with peptidoglycan. does not usually have a nucleus.

A Eukaryotic cell has membrane bound organelles. 

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.