4. living organisms require energy to function and this includes each and every one of the trillions of cells that constitute the human body. Define in detail and use diagrams appropriate to show how cells extract, use and store energy including but to limited to discussion of cell respiration, glucose, pyruvic acid, glycolysis, krebs cycle, atp, nadh and fadh and electron transport. how much by the complete breakdown of glucose? why is breathing necessary for cellular respiration in animals?