Food is digested, or broken down, so that the nutrients can be extracted for use by the body as it passes through the digestive system. If food wasn't digested you would not have energy required to run vital chemical reactions and eventually resulting death
Cell is our microscopic structure. We have Trillions of cells in our body, which plays very important roll. Our every tissue, organ, organ system, our whole body has composed of cells. In order to make a nice and informed decision for our health, we must need to understand our body at cellular level
Hope this helps!