DidacBiol

Annie Champagne Queloz, PhD. ETH Zürich

DidacBiol

“Energy is required to perform a work” is meaningless in biology education

Energy

“Energy is required to perform a work.”

In an university introductory biology course, I have investigated undergraduates’ thinking about the concept of energy. The question was simply: “Define energy”. This question was simple in construction in order to avoid influencing students’ answers (Schurmeier et al. 2010). In addition, I was curious to find out the discipline influence in the student’s reasoning. The most popular explanation was “energy is required to perform a work”, mainly inspired by knowledge learned in physical courses. In biological contexts, such reasoning doesn’t really help to understand the energy requirement in biological processes. For example, understanding molecular binding of medicaments or antibodies requires the recognition of energetic properties of molecules and understanding some thermodynamics principles (more details here). “Perform work” is quite meaningless in such microscopic scale. Cooper and Klymkowsky (Cooper & Klymkowsky 2013) consider that the focus on macroscopic events in physics courses (the most classic example is an object rolling down a hill) harms to develop an interdisciplinary understanding of this concept, mainly in biology introductory courses. This problem is referred as multimodalities in representing the concept of energy (Tang et al. 2011). Indeed, differences in discourse between disciplines make the concept energy confused for many students (Hartley et al. 2012).

Energy?

How can we define clearly energy that may help students to improve their biological understanding? Let’s check on Wikipedia.

“In physics, energy is the property that must be transferred to an object in order to perform work on – or to heat – the object, and can be converted in different forms, but not created or destroyed. […]. Common energy forms include the kinetic energy of a moving object, the potential energy stored by an object’s position in a force field (gravitational, electric or magnetic), the elastic energy stored by stretching solid objects, the chemical energy released when a fuel burns, the radiant energy carried by light, and the thermal energy due to an object’s temperature”. (Wikipedia)

“In biology, energy is an attribute of all biological systems from the biosphere to the smallest living organism”. (Wikipedia)

Hartley and al. (2012) have investigated energy definitions in popular chemistry, physics and biology textbooks (Figure 1).

Hartley

Figure 1: Textbook definitions and index-term usage of energy and matter (from Hartley et al. 2012)

We can notice that the idea of capacity to do work, the form of energy (potential, kinetic, heat, thermal energy), conservation of energy are common terms among chemistry, physics and biology textbooks. However, we mainly retain that energy is an abstract concept, not observable and impossible to measure directly. To cite Richard Feynman (1963), “It is important to realize that in physics today, we have no knowledge of what energy is“. In 2017, the definition is not really more elaborated. Energy is still a hard concept to teach and to learn. If we cannot easily define it, maybe we can analyze the potential origin of the confusion.

Interdisciplinary Confusion

As we can see, energy is a core concept in education of sciences. Energy underlies all processes in physics, chemistry and biology. The main problem in biology courses is that many students do not consider energy as the main driver of molecular interactions. It includes movements, binding and detachments of molecules in cells. Such interactions directly influence, for example, expression of genes and consequently, the determination of morphological traits. Students often restrict their reasoning by having a macroscopic view of physical principles. For examples, a ball rolling down a hill (kinetic vs potential energy) or the energy requires to maintain muscles in action. In addition, many research demonstrated that students have many misconceptions on the concept of energy (entropy, potential/kinetic energy) (Neumann et al. 2012; Haglund et al. 2015; Geller et al. 2014). It might be possible that such misconceptions are transferred into biological contexts. Megan Nagel and Beth Lindsey (Nagel & Lindsey 2015) have shown that students who leaving an introductory general chemistry course do not recognize how distance between molecules are determinate by the energy of a system. We know that many students struggle to understand how molecules “find each other” or get apart again (Klymkowsky et al. 2010; Champagne Queloz et al. 2016).

In parallel, the misconceptions “energy is stored in chemical bonds” and “energy is released when bonds break” is well popular among the learners. It indicates that students often consider chemical bonds as a physical entity.

“This notion of a chemical bond as matter thus appeared to be linked to the everyday notion that building any structure requires energy input, and its converse, destruction, releases energy, to form the basis for the prevalent alternative conception that bond making requires input of energy and bond breaking releases energy”. (Boo 1998) p. 574

In biology contexts, there is this false idea that breaking chemical bonds of food by digestion (in other words, a catabolism reaction) releases energy. The focus should be on the chemical reactions. Precisely, the reaction between oxygen and the food through the cellular respiration transforms the potential energy into chemical (ATP) and thermal (heat) energy. This thermal energy is essential to govern all biological processes.

The thermodynamics factor, the thermal energy, is the “force” pushing the molecules in diverse directions, engendering collisions and then, causing random movements of its. Hartley et al. (2012) reported that in the majority of biology textbooks, the focus is on movement, i.e. the transfer through ecosystems and transformations of energy. In their investigation, they found that only few textbooks were referring to the conservation of energy or law of thermodynamics to describe biological processes.

There is another problem. In chemistry and physics courses, energetic models are most of the time presented in equilibrium closed-systems, or in controlled-environmental systems. In contrast, biological systems are open, i.e. there are exchanges between organisms and the exterior environment. The exchanges consist of continuous building up and breaking down of molecules (Bertalanffy 1950). Here you can find fancy explanations about this principle.  Again, such energetic exchanges take origin in thermodynamics processes.

Some solutions?

The concept of energy is difficult to teach because there is not explicite consensus among scientific disciplines. Hartley and al. (2012) paper gives some insights helping to be aware of the interdisciplinary confuse meaning of energy. According them, simply to increase the awareness of the differences in how biologist, chemists and physicists define energy might help to better teach it. It also improve understanding of students.

Moreover, students need help to make spontaneous connections between knowledge taught in physics, chemistry and biology classes (Nagel & Lindsey 2015; Tang et al. 2011). Megan Nagel and Beth Lindsey (Nagel & Lindsey 2015) showed that only few of them have the abilities to transfer their knowledge through different disciplines.

energydrinks

Figure 2: Some students can think that energy is a physical entity, such a liquid or a solid.

The last point is about the terminology used to describe energy. Everyday language can conduct through a wrong understanding of this concept. For example, we often read, “chemical reactions produce/create energy”. The energy is transferred or transformed, but it is never produce or create. This wrong idea is again the first law of thermodynamics, the conservation of energy. Another example is the use of the word “substance” to define energy. Some students can think that energy is a physical entity, such a liquid or a solid. Moreover, some consumable products, such energetic drinks or energetic bars increase the prevalence of this “substance” thinking. Such everyday expression should be used carefully when the concept of energy is taught.

Conclusions

As you can see, teaching and learning energy takes a lot of energy! Only awareness of such difficulties can make it easier, I think. The general idea of that post was that, to inform about some issues and unfortunately, not to give a precise definition of this interdisciplinary concept. I have the humility to recognize that it’s definitely over my scientific competencies!

References

Bertalanffy, von, L., 1950. The theory of open systems in physics and biology. Science, 111(2872), pp.23–29.

Boo, H.K., 1998. Students’ understandings of chemical bonds and the energetics of chemical reactions. Journal of Research in Science Teaching, 35(5), pp.569–581.

Champagne Queloz, A. et al., 2016. Debunking Key and Lock Biology: Exploring the prevalence and persistence of students’ misconceptions on the nature and flexibility of molecular interactions. Matters Select, pp.1–7.

Cooper, M.M. & Klymkowsky, M.W., 2013. The Trouble with Chemical Energy: Why Understanding Bond Energies Requires an Interdisciplinary Systems Approach. CBE-Life Science Education, 12(2), pp.306–312.

Geller, B.D. et al., 2014. Entropy and spontaneity in an introductory physics course for life science students. American Journal of Physics, 82(5).

Haglund, J., Andersson, S. & Elmgren, M., 2015. Chemical engineering students’ ideas of entropy. Chemistry Education Research and Practice, 16(3), pp.537–551.

Hartley, L.M. et al., 2012. Energy and Matter: Differences in Discourse in Physical and Biological Sciences Can Be Confusing for Introductory Biology Students. BioScience, 62(5), pp.488–496.

Klymkowsky, M.W., Underwood, S.M. & Garvin-Doxas, K., 2010. Biological Concepts Instrument (BCI): A diagnostic tool for revealing student thinking. arXiv.org.

Nagel, M.L. & Lindsey, B.A., 2015. Student use of energy concepts from physics in chemistry courses. Chemistry Education Research and Practice, 16(1), pp.67–81.

Neumann, K. et al., 2012. Towards a learning progression of energy. Journal of Research in Science Teaching, 50(2), pp.162–188.

Schurmeier, K.D. et al., 2010. Using Item Response Theory To Assess Changes in Student Performance Based on Changes in Question Wording. Journal of Chemical Education, 87(11), pp.1268–1272.

Tang, K.S., Tan, S.C. & Yeo, J., 2011. Students’ Multimodal Construction of the Work–Energy Concept. International Journal of Science Education, 33(13), pp.1775–1804.

 

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