Learning of concepts in biology can be made effective by providing historical perspectives, social context and inclusion of laboratory exercises in regular teaching practice. Among laboratory exercises, biochemical experiments prove to be useful tools to promote biology as a subject of logical reasoning requiring analytical skills. One such investigation of an enzyme-catalyzed redox reaction is presented here. This investigation was carried out by a selected group of high school students. At the end of the experiment, the procedural and conceptual understanding of students was probed using specially designed multiple-choice questions (MCQs). Students' responses to MCQs and experimental readings reflected their skills such as understanding about appropriate controls, hands-on skills, and procedural understanding. Analysis indicated that 57% of the students demonstrated Lower Order Cognitive (LOC) skills while only 23% of the students demonstrated Higher Order Cognitive (HOC) skills. Students' responses indicated that their procedural understanding varied between 14-50%, while hands-on skills were in the range of 27-41%. This shows the need of such laboratory practices in regular biology curriculum. Inclusion of this experiment as a guided inquiry in the regular curriculum can help students enhance their HOC skills.
In Japan, elementary school children have been using their own saliva for experiments on starch digestion when they learn about the digestion and absorption of food in science. In carrying out these experiments, the use of their own saliva is particularly important for pupils, because they can notice that their own digestive juices digest food inside their digestive organs. However, various germs may be contained in saliva, so that considerable caution is required to avoid infectious diseases. In addition, pupils dislike providing their saliva for these experiments. To overcome such obstacles, we have introduced a step, the preparation of saliva enzyme powder by the cold ethanol precipitation method, into the experimental procedure. Since the ethanol precipitation technique is too advanced for pupils, this step must be done by the teacher as a demonstration of the method. In our trial of the laboratory class on starch digestion, at first, a solution of the saliva enzyme powder, which the teacher had prepared, and a sheet of starch-containing paper were used to confirm that the saliva enzyme powder could digest starch. Then, pupils were given a question, “Do living things other than human beings also contain digestive aids to digest starch?” To find an answer to the question, pupils examined whether starch digestion would occur by the crude enzyme powders from germinating corn grains and “kome-koji” (malted rice with Aspergillus sp.) which were prepared by the same method as the saliva enzyme powder. In their experiment, small polythene bags and plastic straws were used instead of test tubes and syringes, respectively, to reduce the cost of the experiment. More than four fifths of pupils expressed affirmative impressions of the laboratory class.
Euglena is a common photosynthetic protist, useful as teaching material in biology at secondary and tertiary levels, because it has some unique features of interest to students. Euglena can be cultured in an inorganic medium (HYPONEX solution) without contamination by heterotrophic microorganisms, rendering it suitable for experiments on photosynthesis. In this study, we immobilized Euglena cells in calcium alginate gel beads (“Euglena beads”), facilitating their repeated use in experiments on photosynthesis. In this immobilized state, Euglena could propagate could reproduce in 0.1% HYPONEX solution and gradually turned green under the culture conditions. The Euglena beads were demonstrated to be a useful substitute for aquatic plants, such as Elodea and Cabomba, in the qualitative experiments in which a pH indicator was used to detect photosynthetic CO2 consumption. Euglena beads cultured for 30 days had sufficient photosynthetic activity to allow measurement of photosynthetic rates within 30 minutes.