Metabolic Voyages!

By John S. Peters, Ph.D., College of Charleston, Dept. of Biology

Let me introduce this activity by harkening back to my undergraduate experiences learning metabolism in introductory biology, biochemistry and cell biology.  Perhaps, as a teacher, you'll recognize some the same learning difficulties among your own students.   I remember being thoroughly confused by metabolism.  This incredibly complex intracellular biochemical process which requires a deep and synthetic understanding of energetics, osmosis and diffusion, cell anatomy and biochemisty remained a mystery to me until graduate school.  Up until that time, I had learned about these process primarily through lecture and textbook readings.  These very linear, hierarchically organized, and in the case of lectures, very didactic, expository and "chronological" presentation of metabolism left me with significant holes in my understanding of these processes.  The inaccurate or inadequate meaning I was making had far reaching effects on my conceptual understanding of the larger processes.  In short, I believe these misconceptions kept getting in the way of understanding the big ideas!  Without this broader understanding, I was left with what seemed like millions of tiny details, to be remembered for an exam, and then quickly forgotten.   

This activity is designed to engage students in a metaphorical "voyage" to the organelles (mitochondrion or chloroplasts) involved in cellular respiration and photosynthesis.  During the activity, students adopt various molecular and chemical roles, and literally act out the light-dependent reactions of photosynthesis or the electron transport chains (chemiosmotic ATP generation) of cellular respiration.   Students are then challenged to act out these processes under varying cellular or environmental conditions (low oxygen, nutrient deficiencies etc...).  The activity closes with team-based activity in which students work collaboratively to generate graphical predictions (or interpret data) regarding the effects of cellular manipulations akin to those that were used when scientists were working to elucidate the nature of these metabolic processes.   I find that this process works for students because it follows a well established cycle of learning which is grounded in learning theory.
1) ENGAGE - They are first exposed to a meaningful context in which to explore these metabolic processes (the PBL problems...see below).
2) EXPLORE - They are held accountable for first trying to learn it on their own (textbook reading and PowerPoint Tutorials) by being told, prior to the voyage, that their will be a RAT on the day of the voyage.
3) EXPLAIN - The are afforded the opportunity to apply concepts they've learned from the text, first, in a concrete way (seeing it happen during the Voyages) and then...
4) ELABORATE - Multiple attempts to "act out" the processes with students changing roles, and under different cellular conditions helps students understand how scientists elucidated these complex biochemical processes, and affords them the opportunity to connect metabolism to the problem.
5) EVALUATE - They are afforded the opportunity to evaluate their understanding of the process by applying what they learned to the more abstract process of making predictions or analyzing data which requires the use of concepts learned in the voyage.

Using Interactive Voyages in the Context of a PBL Class

In a PBL class, these voyages are done in the context of the problem we are working on (i..e Cellular Respiration - Mitochondria, Metabolism and Athletic Performance: Blood Boosting in Sports or for Photosynthesis - The Geritol Solution).  Students are asked to come to "The Voyages" having read the relevant chapters on energetics, membrane transport, and metabolism, after the problem has been introduced and students have identified and begun researching learning issues.  To support their reading they are provided with interactive PowerPoint tutorials which support building conceptual understanding of the larger processes involved in metabolism.   I don not lecture on metabolism prior to the voyages at all...even in the non-major's courses!  We do however, follow-up the voyages with an interactive lecture and/or concept mapping activity.  I use this activity in BOTH my majors' and non-science majors' introductory classes.  In fact, I often find that my non-majors, are better at this then the biology majors!

Planning for the Voyage
This activity is typically done best outside on a nice day.  On my campus I have located two areas that are well suited to this activity.  For the chloroplast voyage, we use a large raised cistern as a thylakoid (figure 1a). For the Voyage to the mitochondrion, we have a sunken picnic area behind our student center which serves nicely as a mitochondrion (see figure 1c).   Alternatively, an auditorium stage (with stairs) works nicely as an indoor venue for these activities (figure 1b).  The voyage and follow-up assessment activity usually and be completed in a 1 hr and 15 minute class period.  Some videos of the voyages are presented at the end of this activity description.

Figure 1.  Venues for the voyages at our college. 
 a) Chloroplast Voyage (raised cistern)
b) ChloroplastVoyage (inside the auditorium) c) Mitochondrion Voyage (sunken picnic area)

The Day of the Voyage