This is a semester-long project-based cell biology laboratory course designed to develop scientific thinking skills in undergraduates. In this laboratory course, the students learn to construct testable hypotheses, to quantitate and evaluate the significance of results, and to relate their research to what is currently known. These research concepts are developed around the principal investigator's area of research expertise, cell membranes. One of three semester-long laboratories are offered each year, dealing with either differential protein solubilization from membranes, hormone-receptor interactions, or effects of lipid environment on membrane protein activity. The equipment requested, a high-speed refrigerated centrifuge, is necessary for these studies. The project directs students away from simply memorizing concepts and leads them to understand and then to apply scientific approaches to biological problems.