Experts in the biomolecular sciences use a variety of external representations (ERs) to discuss research. These ERs represent enzymatic systems in myriad ways, ranging from undetailed basic shapes to intricate, stylized three-dimensional representations. However, likely due to this intense variety, student-novices experience extensive confusion when interacting with such ERs in biochemistry, as shown in e.g., ref. 1, among many others. An added layer of complication arises from the fact that enzymes are now accepted to consist of either protein or RNA, which each use unique representational conventions. Our work thus aims to inventory the plethora of representation types in enzyme catalysis representations, with the ultimate goal of consolidating these types, their role in explaining mechanisms2, and implicit conceptual and reasoning skills3, into a student reference tool. To accomplish this, we are conducting a content analysis of enzyme catalysis chapters in four widely used biochemistry textbooks. Our preliminary results define the major types of recurring ERs in instruction of enzyme catalysis. We further find that each facet of mechanistic explanations are explained by multiple types of ERs. Additionally, we find that a single ER can serve as depictions of multiple components of a mechanistic explanation. By describing the trends observed in major textbook images of enzyme catalysis, our work begins to shed light on potential sources of student confusion when interacting with these ERs. The tools we develop based on our results will thus greatly advance students’ progress in interacting with ERs of enzyme catalysis at an expert level.