Constructing explanations is an essential skill for all science learners. The goal of this project was to model the key components of expert explanation of molecular and cellular mechanisms. As such, we asked: What is an appropriate model of the components of explanation used by biology experts to explain molecular and cellular mechanisms? Do explanations made by experts from different biology subdisciplines at a university support the validity of this model? Guided by the modeling framework of R. S. Justi and J. K. Gilbert, the validity of an initial model was tested by asking seven biologists to explain a molecular mechanism of their choice. Data were collected from interviews, artifacts, and drawings, and then subjected to thematic analysis. We found that biologists explained the specific activities and organization of entities of the mechanism. In addition, they contextualized explanations according to their biological and social significance; integrated explanations with methods, instruments, and measurements; and used analogies and narrated stories. The derived methods, analogies, context, and how themes informed the development of our final MACH model of mechanistic explanations. Future research will test the potential of the MACH model as a guiding framework for instruction to enhance the quality of student explanations.


This is the published PDF version of Trujillo, Caleb M.; Anderson, Trevor R.; and Pelaez, Nancy J., "A Model of How Different Biology Experts Explain Molecular and Cellular Mechanisms" (2015). CBE Life Sciences Education, 14(2): 1-13. http://dx.doi.org/10.1187/cbe.14-12-0229.

This article is © 2015 C. M. Trujillo et al. CBE—Life Sciences Education © 2015 The American Society for Cell Biology. This article is distributed by The American Society for Cell Biology under license from the author(s). Two months after publication it is available to the public under a Creative Commons–Attribution–Noncommercial–Share Alike 3.0 Unported License (http://creativecommons.org/licenses/by-nc-sa/3.0).


Explanations, Biology, Mechanisms, Expert, Model, Qualitative, Discipline-based learning research

Date of this Version






First Page


Last Page