This lesson is a sequence of learning activities that support student understanding of the role of enzymes in the digestive system and how the digestive system is supported by the circulatory system to provide nutrients to all cells. The lesson plan is divided into three laboratory activities each with separate probing questions. The first lab activity has background information, experimental procedures, results tables and interpretation questions. Students design their own procedure and data table for the second and third lab activities. Extensive teacher resources are included and are a strength of this lesson sequence. Examples of resources include specific learning goals, teacher background information and flow charts. These three laboratory activities for students are appropriate for high school biology in an introductory unit on biological molecules or as an introduction to a unit on molecular biology.