Undergraduate introductory biology students at the university level often struggle to trace movement of matter and energy through catabolic and anabolic processes in biological systems. A sequential guided simulation of cellular respiration and photosynthesis provides students an opportunity to actively model and visualize matter transformation and energy accumulation and degradation through the movement of molecular and energy “game pieces.” The activity was designed to help students generate a simplified outline of these two highly complex processes, while reinforcing the principles of conservation of matter and energy. My students participated in this activity during peer-led review sessions in an undergraduate, introductory, majors biology course (ca.150 students in 18 SI sessions over two semesters), but instructors could also easily adapt it for use in small lecture or laboratory classrooms, introductory cell biology, physiology, and ecology courses, or with high school students.