Rosa eats a peanut butter sandwich for lunch. Peanut butter contains a lot of protein, and bread is mostly starch. Rosa plans to go for a run later this afternoon. Rosa is breathing normally.

What does she need from the food she ate and the air she breathes so that she can go on her run? How do Rosa’s body systems work together to get the molecules she needs into her cells? How do her cells use these molecules to release energy for her body to run?