Deidre A Tronson

Modelling Photosynthesis to Increase Conceptual Understanding

Biology students in their first year at university have difficulty understanding the abstract concepts of photosynthesis. The traditional didactic lecture followed by practical exercises that show various macroscopic aspects of photosynthesis often do not help the students visualise or understand the submicroscopic (molecular-level) reactions that are occurring within the chloroplast membranes. If students can construct their own complex concepts in small steps, with guidance from lecturers and demonstrators (teaching assistants) to ensure they are not building-in ‘new’ misconceptions, they are more likely to form positive attitudes towards further study and raise their self-esteem about learning strategies. This paper describes a teaching/re-teaching sequence of the light-dependent reactions of photosynthesis that presents the students with a range of learning and teaching approaches. Following a traditional didactic lecture, students have a practical exercise where they make their own models of chloroplasts, reinforced by small-group discussion sessions where they make their own diagram-matic summary. Online resources and textbooks are available for private study. The re-teaching step is an interactive lecture appealing to a range of learning modalities. Using this teaching and learning strategy, students increasingly use metacognitive skills to aid their further understanding of the submicroscopic world of atoms and molecules.

Supercritical Fluid Extraction (SFE) of Monoterpenes from the Leaves of Melaleuca alternifolia (Tea Tree)

The technique of supercritical fluid extraction (SFE) was applied to various sample matrices under a range of supercritical carbon dioxide (scCO2) densities and chamber temperatures. The purpose was to develop an effective extraction condition for the removal of eight target monoterpenes from Australian tea tree (Melaleuca alternifolia Cheel) leaves. The optimum conditions for extraction were found to be 0.25 g/mL scCO2 density at a chamber temperature of 110°C. These condition were most effective when applied to whole fresh and rehydrated whole dried leaves, where it yielded maximum recovery of target analytes with minimum change in oil composition for the extractor system employed. This study demonstrates the importance of the type of sample matrix used in SFE work, and that a different extraction protocol would need to be developed for each matrix.

The Odour, the Animal and the Plant

A review of the literature is presented that gives a background to the human sense of smell, then the importance of learnt and innate olfactory cues in animal behaviour. Some possible roles for natural products chemists interested in the interaction between animals and plants are discussed.