Elvis eats a peanut butter sandwich for lunch. Peanut butter contains a lot of protein, and bread is mostly starch. Elvis plans to go for a run later this afternoon. He is breathing normally. What does he need from the food he ate and the air he breathes so that he can go on his run? How do Elvis' body systems work together to get the molecules he needs into his cells? How do his cells use these molecules to release energy for his body to run?