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Chemistry  Discovering an Accessible Enzyme: Salivary α- Amylase
The complexity underlying enzymes can be difficult for students to grasp because enzymes cannot be easily visualized; school texts tend to describe them in abstract molecular terms and often our students are not capable of the abstract thinking necessary to understand them. With regard to this it is sufficient to remember Piaget's theory of concrete operations preceding formal operations and the Dewey consideration "words can detach and preserve a meaning only when the meaning has been first involved in our own direct intercourse with things". One way for achieving a good level of understanding is to participate in an activity that mirrors biochemical practice.
Isabella Marini has chosen amylases, two enzymes whose catalytic activity can be detected without any instruments except the eyes; moreover they can be easily extracted from germinating barley or the students' own saliva. Starch hydrolysis can be achieved either by inorganic catalysts - which require extremes of temperature and pH - or by our extracts - which perform the same reaction under very mild conditions. By considering this stark difference, students can hypothesise that in living organisms there exists "special and powerful substances", able to catalyse reactions. With some easy, quick and inexpensive laboratory experiments, students grasp what the activity of an enzyme consists of: first in a qualitative then in a semi - quantitative way. They can observe the influence of environmental factors (pH, temperature, substrate concentration, inhibitors presence) on activity, and realise that enzymes are molecular sensors with catalytic power. The heuristic laboratory approach is integrated with theoretical knowledge about amylases and starch, their physiological meaning, biotechnological applications, as well as their importance for human nutrition and influence on painting. Contact details
Last update: 17 July 2007
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