The power house of the cell is

Aerobic organisms are able to capture a far greater propoion of the available free energy of respiratory substrates than anaerobic organisms. Most of this takes place inside mitochondria, which have been termed the "powerhouses" of the cell. Respiration is coupled to the generation of the high-energy intermediate, ATP, by oxidative phosphorylation.Ref: Harper&;s Biochemistry; 30th edition; Chapter 13; The Respiratory Chain & Oxidative Phosphorylation