Students know the sequential steps of digestion and the roles of teeth and the mouth, esophagus, stomach, small intestine, large intestine, and colon in the function of the digestive system.

Food is made of large molecules such as proteins, complex carbohydrates (such as starches), and nucleic acids (such as DNA). Digestion is the process that breaks these huge molecules down into their smaller building blocks. At the end of digestion, the animal that has eaten the food can now use those small building blocks for energy or to build its own huge molecules. The small intestine is the place where these small molecules enter the blood stream so they can circulate to all the cells of the body.