Your mouth chews the food to physically break it down into smaller pieces. These go to the stomach, which uses acid to chemically break down the food into tiny molecules, making a sort of acid-nutrient soup. Your intestines neutralize the acid and begin absorbing the molecules from the "soup." The nutrients go into the blood stream, where they are provided to cells all over your body. Each cell makes its own energy through respiration; it can take a molecule of glucose (simple sugar) and break it down, step by step, into carbon dioxide and water, using some oxygen gas along the way. As it does so, it captures the energy by using those reactions to "energize" certain specific molecules; the cell is able to use these "energized" molecules to "power" other functions.