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Monica L. Tischler
Department of Biological Science
Bendectine University
How to Make ATP: Three Classic Experiments in Biology

This case study for the flipped classroom introduces the discovery process used to elucidate how cells make ATP. Data from three seminal primary literature papers and novel (for their time) methods are used to illustrate how scientists determined the mechanism of ATP synthesis via chemiosmosis across a membrane. The story begins with the classic reductionist approach used by many brilliant scientists to figure out familiar pathways such as glycolysis and the Krebs cycle. This method worked so well that there was little reason to think that the elusive intermediates in the ATP pathway wouldn't also be similarly revealed. Mitchell (1961) hinted that this classic approach might not work for ATP synthesis; Jagendorf and Uribe (1966) showed that pH changes (a proton motive force) across a membrane can generate ATP, describing the process of chemiosmosis; Racker and Stoeckenius  (1974) described the individual components necessary for ATP synthesis in an artificial system. By taking an historical approach, students learn a basic biochemical concept while also learning that discoveries sometimes take time to be accepted by other scientists.

Tougher Plants: Beating Stress by Protecting Photosynthesis in Genetically Modified Plants

This "clicker case" follows two recent college graduates as they look for scientific answers to explain why the plants on their new tomato farm are not doing well. Working with their agricultural extension agent, they explore the scientific literature and learn how cold, heat, and salt can stress plants. They also learn that plants genetically engineered to produce glycine betaine, a modified amino acid, can withstand the environmental conditions that stress many agricultural plants. In their explorations, the fledgling farmers read graphs from the primary literature and review photosynthetic processes from their introductory biology course. The case consists of a PowerPoint presentation with embedded multiple-choice questions that students answer using clickers.  Developed for a first-year class in biology, it could be used in any lower-level college biology class or potentially an advanced biology class in high school. The case is also accompanied by an optional PowerPoint presentation (see "Supplemental Materials" tab above).