Enzymes
At GCSE, students should appreciate that enzymes are important proteins, essential for reactions to take place. They need to be able to explain the mechanism of enzyme action, including the active site, enzyme specificity and factors affecting the rate of enzymatic reactions.
Misconceptions about enzymes include the idea that enzymes work best at 370C. It is important to make students aware early on in the delivery of this topic that enzymes are found in a variety of organisms which exist in extremes of temperature and do not have a constant body temperature. To ensure that students do not refer to enzymes as "being killed" it is essential that they have an understanding of the structure and concept of an enzyme as a component within a cell so that they are comfortable referring to enzymes being denatured.
Whilst this list provides a source of information and ideas for experimental work, it is important to note that recommendations can date very quickly. Do NOT follow suggestions which conflict with current advice from CLEAPSS, SSERC or recent safety guides. eLibrary users are responsible for ensuring that any activity, including practical work, which they carry out is consistent with current regulations related to Health and Safety and that they carry an appropriate risk assessment. Further information is provided in our Health and Safety guidance.
Using enzymes to make creme eggs
This video demonstrates how to make soft-centred chocolates, using enzymes. Students could carry out this practical and if undertaken in a food safe environment, using food materials and following a scrupulous hygiene regime, produce chocolates that could be eaten.
This practical/demonstration provides a "real-world" application of the use of enzymes, which will be of interest to many students (chocolate!). It would be a good practical to complete at the start of this topic or as a reward at the end of the topic if students can demonstrate appropriate knowledge and understanding of enzyme action.
Upgrading Whey
This practical activity is a good demonstration of the use of immobilised enzymes in biotechnology. The materials give a method for producing whey from milk. Students then use immobilised enzymes to produce glucose from the ‘waste’ whey. Students use a glucose test strip to measure the amount of glucose produced. They can be challenged to optimise the process to see how to get the greatest yield of glucose.
Microscale investigations of catalase activity in plant extract
This is a relatively straightforward practical activity that allows students to compare catalase activity across a range of different fruits and vegetables. The protocol uses a deceptively simple, yet very accurate, method to measure the rate of reaction by collecting the oxygen evolved as a product of the reaction.
The whole reaction can be carried out on a very small scale, in a centrifuge tube.
An enzyme extract is adsorbed to filter paper discs. These discs initially sink in a hydrogen peroxide solution, but then float to the surface as the oxygen produced gets trapped in the paper fibres. The time taken for the discs to rise is measured.
As the protocol uses small samples of tissue it is also possible for students to take a series of samples across one particular plant organ (for example a diseased vegetable) and investigate the difference in catalase activity in different areas.
Investigating the effect of pH on amylase activity
This is a standard protocol for this investigation, which is a required practical activity for GCSE Biology students. The Nuffield Foundation link here provides a student sheet with questions and answers (remember to remove the answer sheet before handing out to students).
Having completed the practical in class, the questions would provide a useful homework for students.
Jelly Liquidiser
This video shows how pineapple is able to liquify a bowl of jelly due to enzyme action.
Using the video (without the commentary), a teacher led demonstration or getting students to complete this practical would then lead to a set of useful questions:
What is causing the jelly to liquify?
Why would pineapple have this ability? What possible use could it be?
Would it work with tinned pineapple-why would using this make a difference?
One half of the class could try the experiment with fresh pineapple and one half with tinned.
Converting Milk Products Using Lactase
In this practical students investigate the treatment of milk with lactase. Following treatment of the milk students then test the glucose content of the converted milk products, and compare products of frozen converted and non-converted milk samples.
Different groups (pairs) of students could also be given different types of milk to use (Full fat, semi skimmed, skimmed), so that class results could be compared. The equipment is a little tricky to set up, but should provide some worthwhile results for effective evaluation.
Students are given useful guidance about what to include in their evaluation and there are some challenging questions for them to answer.
RADAAR framework - How I teach enzymes
This infographic gives ideas on how to teach enzymes to 14-16 year olds using the RADAAR (research, anticipate, diagnose, address, assess, review) framework developed by the Best Evidence Science Teaching (BEST) project based at the University of York.
