Core chemistry ideas can be useful tools for explaining biological phenomena, but students often have difficulty understanding these core ideas within general chemistry. Connecting these ideas to biologically relevant situations is even more difficult. These difficulties arise, in part, from a lack of explicit opportunities in relevant courses for students to practice connecting ideas across disciplines. We are developing activities that examine students' abilities to connect core chemistry ideas with biological phenomena, the overall goal being to develop a set of assessments that ask students to connect their knowledge across introductory chemistry and biology courses. Here, we describe the development and testing of an activity that focuses on concepts about energy in bond breaking, bond forming, and ATP coupling. The activity was completed by 195 students in an introductory cell and molecular biology course at Michigan State University; students were either co-enrolled or previously enrolled in General Chemistry I. Follow-up interviews to assess the validity of the activity (among others) showed that students interpreted the questions as intended and that they valued the activity as an opportunity to connect ideas across courses.