"However he explained how the activation energy is like a hurdle and the glucose going through Cellular Respiration is like a hurdler; The hurdle is to high for the hurdler to jump at first, then the official (the enzyme) lowers the hurdle and the hurdler can make it. He used this analogy to show me how cellular respiration needs too much energy to start outside the body but once in the stomach the enzymes make it easier for the reaction to start."