Visual representations of energy and chemical bonding in biology and chemistry textbooks: A case study of ATP hydrolysis.

Energy is a crosscutting concept in science, but college students often perceive a mismatch between how their biology and chemistry courses discuss the topic. The challenge of reconciling these disciplinary differences can promote faulty reasoning-for example, biology students often develop the incorrect idea that breaking bonds is exothermic and releases energy. We hypothesize that one source of this perceived mismatch is that biology and chemistry textbooks use different visual representations of bond breaking and formation. We analyzed figures of ATP hydrolysis from 12 college-level introductory biology textbooks and coded each figure for its representation of energy, bond formation, and bond breaking. For comparison, we analyzed figures from six college-level introductory chemistry textbooks. We found that the majority (70%) of biology textbook figures presented ATP hydrolysis in the form "one reactant → multiple products" and "more bonds in reactants → fewer bonds in products". In contrast, chemistry textbook figures of the form "one reactant → multiple products" and "more bonds → fewer bonds" were predominantly endothermic reactions, which directly contradicts the exothermic nature of ATP hydrolysis. We hypothesize that these visual inconsistencies may be a contributing factor to student struggles in constructing a coherent mental model of energy and bonding.