Diane J Grayson, MASTEC ... using a framework developed by Grayson et al. ... concepts can seriously interfere with the learning of science (White, 1988).
PoS1-4
Identifying students' conceptual and reasoning difficulties with biochemistry Trevor R. Anderson, University of Natal L. Gail Crossley, Australian Catholic University Diane J Grayson, MASTEC Abstract. In this paper we shall describe several student difficulties with concepts and reasoning involved in introductory biochemistry. The difficulties were identified using a framework developed by Grayson et al. (1997). Two difficulties related to students’ understanding of how metabolic pathways function. In one situation, students incorrectly use localised reasoning, while in another they indicate that they do not understand the need for all metabolites to be present for a pathway to proceed. Another difficulty involved confusing certain constants and their related variables by suggesting that the value of the constants could be changed. Students also confused certain quantities with the change in those quantities, sometimes using the two interchangeably. Problems in differentiating between the everyday meaning of „spontaneous“ and the biochemical meaning were also evident. Aim. While the identification of student difficulties in physics, chemistry and biology has been a major area of research for many years, very little has been reported on student difficulties with biochemistry. This is despite the fact that biochemistry is an important requirement for students in the life sciences in many universities, and is very cognitively demanding, both in terms of conceptual complexity and the scientific reasoning required (Wood, 1990). Research on student difficulties has been motivated by the view that, according to the constructivist theory of learning, students construct their own conceptions, and those conceptions that differ from scientific concepts can seriously interfere with the learning of science (White, 1988). Thus it is vitally important that such alternative conceptions are identified and addressed when designing science instruction and curricula (Treagust, et al., 1996). In this paper we shall describe various student difficulties which we identified within the topic of metabolism, especially with respect to glycolysis and oxidative phosphorylation. Study design and methodology. The study was conducted with 142 students enrolled in an introductory biochemistry course at the University of Natal. The course includes a four-week module on glycolysis, followed by a six-week module on oxidative phosphorylation. Prior to these modules students had been introduced to thermodynamics and enzyme kinetics and their application to metabolic reactions. Student difficulties were identified by analysing responses to pretests, tutorials, tests, examinations and interview questions. The two biochemists amongst us (TA and GC) agreed in advance on what they considered to be correct answers. Student responses which were not compatible with these answers were separated out and sorted into groups according to the nature of the difficulty displayed. The four-level framework of Grayson et al. (1997) was used to categorize the student difficulties according to the amount of information available about each difficulty. Difficulties classified at level 4 are termed „established“ because they have been widely documented in a variety of contexts, those at level 3 are „partially established“ because there is some, limited documentation about them, those at level 2 are „suspected“ on the basis of teaching experience but have not been documented, and
PoS1-4 those at level 1 are „unanticipated“ since they emerge unexpectedly. Findings. A. Difficulties with the functioning of metabolic pathways. A metabolic pathway consists of a series of consecutive, linked chemical reactions in which every metabolite (including all substrates, products, enzymes and co-enzymes) needs to be present and functional for the metabolic pathway to occur. In this context, we have identified two related difficulties which we have termed, „essential nature“ and „localized reasoning“. Both difficulties were exhibited in response to questions on the effects of irreversible inhibition of a specific enzyme in a pathway. In the case of the „essential nature“ difficulty, students typically indicate that the affected reaction will continue to occur regardless of the inhibition of its enzyme. This suggests a difficulty understanding the essential functional role of an enzyme as a catalyst under cellular conditions. By contrast, in the „localized reasoning“ difficulty, students might correctly acknowledge that the inhibited enzyme reaction will no longer occur, but incorrectly indicate that this will have no effect on the rest of the pathway. This suggests that the students are only focussing on the local effects, and not the global effects of the enzyme inhibition. A similar reasoning difficulty was identified by Cohen et al. (1983) in the context of electric circuits. Both of these difficulties were also observed in an earlier study (Anderson & Grayson, 1994), but have not yet been identified in a wide variety of contexts. They are thus classified as partially established (level 3). B. Confusing constants and variables. Questions asking students about the effects of inhibiting a certain enzyme-catalyzed reaction revealed a confusion between the constants, Keq (the equilibrium constant) and Vmax (the maximum rate of enzyme activity) and the related variables, mass action ratio (Γ) and actual enzyme activity, respectively. The variables are dependent upon cellular pH, temperature and substrate concentrations. In particular, some students indicated that the values of the constants, rather than that of the variables, would be affected by enzyme inhibition. Since this difficulty emerged unexpectedly in the analysis of the data, we have classified it as unanticipated (level 1). It will be treated as suspected (level 2) in future investigations. C. Confusing a quantity with the change in a quantity. Calculations for biochemical redox reactions sometimes involve the value of a function, such as the redox potential (E), while at other times the change in the function (∆E) is needed. In a variety of assessments, students confused such quantities with the change in the quantities, sometimes using them interchangeably. This difficulty was also unanticipated and classified at level 1 on the framework. D. Confusing everyday meaning of „spontaneous“ with biochemical meaning. When asked to explain the meaning of a spontaneous reaction, 91% (129/142) of students described it as one which can proceed or occur freely on its own without external stimuli. This is not surprising, given that in everyday speech, „spontaneous“ means „acting or done or occurring without external cause“ (Concise Oxford Dictionary). Indeed, McPartland and Segel (1986) noted similar interpretations amongst chemistry students. This difficulty can thus be considered partially established (level 3), since some documentation exists but it is not extensive.
PoS1-4 Implications. We have begun to systematically investigate and document student difficulties in biochemistry. As with other disciplines, it is clear to us that a number of distinct difficulties exist. At this early stage of the work only preliminary results can be presented about the nature and prevalence of specific difficulties. However, using our framework, we intend to focus the probes we already have and to design new ones in order to clarify the nature of student difficulties in biochemistry and establish their prevalence. Once that process is further along the road, we intend to investigate the roots of the difficulties thus identified and to try to design instruction to remediate them. References. Anderson, T.R & Grayson, D.J. (1994). Improving students’ understanding of carbohydrate metabolism in first-year biochemistry at tertiary level. Research in Science Education, 24, 1-10. Cohen, R., Eylon, B. & Ganiel, U. (1983). Potential difference and current in simple electric circuits. American Journal of Physics 15 (5), 407-412. Grayson, D.J., Anderson, T.R. & Crossley, L.G. (1997). A multi-level framework for identifying student difficulties in a little-researched discipline area (Biochemistry). In M. Sanders (Ed.), Proc. 5th Annual Meeting of SAARMSE, Univ. Witwatersrand, 2226 January, pp. 118-124. McPartland, Ann A. & Segel, I. H. (1986). Equilibrium constants, free energy changes, and coupled reactions: concepts& misconcepts. Biochemical Education 14(3),137-141. Treagust, D.F., Duit, R. & Fraser, B.J. (1996). Overview: Research on students’ preinstructional conceptions, In Treagust, Duit and Fraser (Eds.), Improving Teaching and Learning in Science and Mathematics. Teachers College Press: NY, pp. 1-14. White, R.T. (1988). Learning Science. Oxford: Blackwell. Wood, E.J. (1990) Biochemistry is a difficult subject for both student and teacher. Biochemical Education 18 (4),170-172.
