Teaching enzymes to pre-service science teachers through POE (predict, observe, explain) method: The case of catalase

It is reported that use of laboratory in science teaching practices allows students to participate in science education and teaching process actively, form new opinions about subjects they wonder through personal observations, establish relationships between concepts, learn ways of reaching scientific truths, use the theoretical knowledge they acquire in their daily lives, take part in research that involves their thoughts and efforts, gain concrete learning experience, and develop positive attitudes towards science lessons (Atasoy, 2002; Ayvacı and Küçük, 2005; Tekin, 2008a; MEB, 2013). Thus, laboratory practices are expected to allow establishing a meaningful relationship between the theoretical knowledge acquired in the classroom environment and what is observed during laboratory works, incorporate students in the process of constructing knowledge, increase meaningful learning, assign responsibility to students for their own learning, encourage students, and make them regard laboratory as a real learning environment.

It is reported in some studies that a lot of difficulties are faced during laboratory practices and that laboratories are far from providing a meaningful learning environment as students mostly fail to understand the relationship between their observations in the laboratory and theoretical knowledge (Friedler and Tamir, 1990; Erten, 1991; Gürdal, 1991; Nakhleh and Krajcik, 1993; Alpaut, 1993; Ayas, Çepni and Akdeniz, 1994; Ekici, 1996; Uluçınar et al., 2008; Akgün, 2010; Olympiou and Zacharias, 2011; Lowe, Newcombe and Stumpers, 2012).

An issue that increases problems and misconceptions more is that students do not have enough understanding of such basic concepts of scientific research process as formulating a hypothesis, observation, and data, are incompetent in practice, have problems in observing events, recording data, and making inferences, and do activity and draw conclusions without considering the relationships between variables. It is thought that if students comprehend and use these processes properly, laboratories that provide students with an efficient learning environment will serve as quite suitable environments for science teaching. It is reported that use of laboratory contributes to scientific knowledge bases and scientific process skills of students (Tamir, 1998; Hofstein and Lunetta, 2004; Morgil, Güngör and Seçken, 2009; Böyük, Demir and Erol, 2010; Sarı, 2011; Pekbay and Kaptan, 2014). When all these positive aspects are taken into consideration, the POE method confronts us as one of the effective methods of minimizing limitations in laboratory use.

The POE method, which is based on constructive approach and effective in improving quality in learning, allows students to apply what they learn in science laboratories or activities in the field and establish a link between their knowledge and natural events they encounter in their daily lives. The POE method is implemented in 3 stages. The first stage involves teaching the determined subject to students theoretically and requesting them to make predictions about the subject. In the second stage, activities are done, and students are expected to make observations. In the third stage, students are requested to explain differences or similarities between their predictions and their observations (Çepni, 2011).

It is stated that the POE method is an approach that activates students’ prior knowledge, leaves the resolution of contradictions concerning their observations to them, ensures that its steps are performed without skipping any of them, and is preferred because it is highly appropriate and easy to use (Yıldırım et al., 2004; Tekin, 2008a). Being an effective learning approach, the POE method is very suitable for teaching certain subjects and concepts in experimental and practical lessons. However, it is evident that there are some subjects and concepts for teaching which the POE method is not appropriate, which is not surprising as there is no teaching method that fits the teaching of all subject and concepts. Regarding the stages of the POE method only as experimental steps restricts its use as a teaching method. Another problem is that it is not possible to make observations based on assumptions in some of the experiments in which the POE method is to be employed.

Literature review shows that biology research employing the POE method focuses on osmosis (Çimer and Çakır, 2008); biological reproduction (Wu and Tsai, 2005); respiration and photosynthesis in plants (McGregor and Hargrave, 2008; Köse et al., 2003); substance transport in plants (Bilen and Köse, 2012); use of microscope, examination of animal and plant cells, plasmolysis and deplasmolysis, osmosis and diffusion, plant tissues, factors influential on photosynthesis and transport in plants (Bilen and Aydoğdu, 2012); growth and development in plants (Bilen and Köse, 2012; Tokur, 2011); substance pass through the cell membrane (Harman, 2014; 2015); circulatory system (Demirelli et al., 2008); and environmental education (Güven, 2011; 2014).

Though certain difficulties are confronted in the implementation of the POE method, the above-mentioned studies indicate that observing after predicting is effective in learning; students learn better and correct their existing misconceptions through POE activities; the POE method attracts the attention of students to experiments; it helps students understand experiments better and thus promotes conceptual understanding; it may enrich evidence-based experiments conceptually; students learning through POE activities are more successful and have more positive attitudes; and the POE method creates contradictions in students’ minds while learning new concepts and then allows them to achieve meaningful learning by comparing their predictions with their observations.

Enzymes are one of the biology subjects in teaching and learning which individuals have difficulty (Bahar et al., 1999a; Bahar, 2002). Two of the fundamental difficulties experienced in understanding enzymes are as follows: enzymes have an abstract aspect; individuals fail to comprehend the integrated operation of such a high organizational order in the living environment. It is known that misconceptions about enzymes include their concrete aspect, conceptual framework, structural characteristics, mode of operation, functions, and types, the factors influential on their operations, enzyme kinetics, specificity, enzyme-substrate complex, and enzyme-metabolism relationship and mostly result from acquisitions in the daily life (Atav et al., 2004; Emre and Yılayaz, 2006; Selvi and Yakışan, 2004; Sinan, 2007; Sinan et al., 2006; Linenberger and Bretz, 2012; Orgill and Bodner, 2007; Marini, 2005; Kurt, 2013; González-Cruz et al., 2003; Voet et al., 2003).

Previous research has mostly focused on determining misconceptions on the subject of enzymes. Though there are some studies dealing with the teaching of enzymes, they use V-diagrams, analogies, and word association methodology (Atılboz and Yakışan, 2003; Şahin, 2002; Güler and Sağlam, 2002; Selvi and Yakışan, 2004; Atav et al., 2004).

Fewness of the number of studies on the teaching of enzymes, which are one of the biology subjects students have difficulty in understanding, (Pfundt and Duit, 2007) and lack of research dealing with the teaching of enzymes through the POE method show the necessity of carrying out a study of this sort. In this regard, the objective of this study is to assess the effectiveness of using POE method in teaching enzymes. Catalase was used for the teaching of factors influential on the operation of enzymes by use of plant and animal structures. H₂O₂ was employed as a substrate.