After the products ofdigestion are taken in by the body, some are stored, some are changed into other molecules. Others come together and form giant molecules. Still others are broken down into still simpler molecules which are passed out.All the chemical changes undergone by these substances in the body make up together what we call metabolism.
One important part of metabolism is the combination of certain molecules with oxygen.This is important be-cause the combination makes energy needed by all the cells of your body.The cells use the energy to break down large-molecules and build up others. Energy keeps your mus-cle cells contracting and your nerve cells carrying impulses. These processes and many more must have energy to occur.
All living things need energy, but you have a special need for energy during your years of quick growth. As you grow, food must supply the building blocks for new tissue and the energy to build new tissue.You also need energy because you are so active.Now can you explain why you always seem hungry?
If you eat properly, your digestive system works well nearly all the time. The system is rarely empty.It works smoothly as it cooperates with all the other systems in your body.
Sometimes, of course, your digestive system works against you.You may get a bellyache. That is only sometimes, however.For the most part, from day to day. the hard-working digestive system keeps you well-supplied with the raw materials and energy you need for life.
