The enzyme ribose 5-phosphate isomerase (RpiA) has many features that make it attractive as a focal point of a semester-long, advanced biochemistry laboratory for undergraduate students. The protein can easily and inexpensively be isolated from spinach using traditional purification techniques. Characterization of RpiA enzyme activity can be assessed using a timed Dische assay or a relatively simple A[subscript 290] kinetic assay. Cloning of the enzyme from "Escherichia coli" works well as a molecular biology exercise to give students experiences in such techniques as polymerase chain reaction, restriction mapping, plasmid purifications, and cell transformations. The use of a common theme throughout the semester more appropriately models the research process and gives the student a better understanding of the procedures included in the pedagogy. (Contains 2 tables and 1 figure.)