If you get a career in any medical field then it's important to know about the functions of the body systems. Knowing about how they work will prepare you for what you need to know when you get that job. Learning these things in school helps prevent you from struggling with your career.
Protein helps build muscle and provide energy
The respiratory system can be damaged from smoke inhalation and tar buildup from the chemicals used in tobacco, which can also harm the heart and blood vessels. Two conditions that can be caused from smoking are Heart Disease and Lung Cancer.