I began including nutrition & digestion in my biochemistry unit in order to help my students draw the kind of 'big picture' connections emphasized by the new AP Biology curriculum. I introduce the material after my lesson on macromolecules, because it allows students to investigate where the raw materials necessary to build these complex molecules come from. This lesson includes a section of guided notes on nutrition, and then requires students to create a labeled diagram of the digestive system and answer questions about the relationships between structure and function in the digestive system. This activity can be done individually, but I usually allow students to work in groups to allow for differentiation - a visual/tactile student can create the diagram while a more verbal student can research the questions. I include a scoring tool that I've used to assess the final outcome. As an assessment, I like to recreate a large version of the diagram on the board, randomly assign students terms, and have them organize a review of where and when each term should be introduced.