In an increasingly complex world, it is imperative that undergraduate science courses prepare students to make confident, informed decisions and predictions. The research presented in this thesis focuses on supporting students to engage in mechanistic reasoning (MR) about phenomena in chemistry and biology (that is, thinking about how and why these phenomena occur). Using a resources perspective of student knowledge construction, I investigated and characterized explanations for two phenomena: (1) preferential protein-ligand binding, leveraging ideas about electrostatic forces and interactions; and (2) ATP-driven coupled reactions, leveraging ideas about energy, reactivity, and favorability. We collected and analyzed over a thousand student responses for the protein-ligand binding task, a previously developed task that elicits productive student ideas and MR as a thinking strategy. Students across chemistry and biology courses engaged in MR to varying extents, but the responses that were fully mechanistic nearly always correlated with a correct prediction, suggesting the predictive power of this reasoning strategy. With a large selection of responses and access to demographic characteristics, I then calculated an ordinal regression model to determine if GPA, race/ethnicity, and/or binary gender predicted student engagement in MR. Binary gender identification did not contribute as a predictor; however, students with a higher GPA had significantly higher odds of engaging fully in MR, and being White (compared to Non-White), to a lesser extent than GPA, also resulted in higher odds of engaging fully in MR. In subsequent studies, I investigated student and instructor understandings of the role of ATP, an integral biological molecule that is directly related to energy, a core idea in both chemistry and biology, suggesting another opportunity for interdisciplinary learning. Due to the widespread misconception that breaking bonds releases energy, which is frequently associated with language about the “high-energy bond(s)” in ATP, we aimed to uncover a more coherent, mechanistic way of talking about ATP. To do this, we first interviewed a range of chemistry, biology, and biochemistry faculty to learn how they explain and teach the mechanism by which ATP provides energy. The findings from this study informed my final study, in which we designed a task that supports students’ understanding of the mechanism by which ATP drives the unfavorable formation of glutamine from glutamate and ammonium. We focus specifically on the role of ATP in transferring a phosphoryl group to create a reactive intermediate, avoiding the common, yet irrelevant, ideas about ATP hydrolysis and bond energy. After working through this task, both molecular biology and organic chemistry students included more mechanistic resources in their final explanations about the role of ATP, suggesting the potential of formative tasks as learning opportunities for students to advance and refine their productive resources. The findings from these four studies point to the challenge, but importance, of incorporating MR into undergraduate science courses. Leveraging interdisciplinary thinking and MR are ways to support making informed decisions as citizens; for example, reasoning about how and why vaccines prevent the spread of infectious diseases, among other reasoning strategies (e.g., social and historical), can support one to make an informed choice. Further, many of the students we serve are pre-health majors, meaning they will pursue careers which often require deep reasoning and understanding about how or why symptoms occur, potential side effects of treatments, and how to appropriately address challenging decisions. MR is an important tool for certain contexts to ultimately help them do this.
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