Respiration and energy: Respiration and breathing are not the same. The purpose of breathing is to provide out cells w ith oxyg en for u se in respiratio n. Respiration is the process of using oxygen to release the energy in the food that we eat. Each of our cells contains tiny structures called mitochondria. This is where respiration takes place. There are many mitochondria in cells that carry out a lot of respiration,such as leg muscle cells, and few mitochondria in less active parts of the body, such as skin cells.