Enzymes
Understanding of enzymes is a fundamental requirement of biology and the key to understanding biological processes and biochemical reactions. Students need to apply their understanding of proteins and chemical bonds to account for the structure and properties of enzymes. They will also need to explain how certain factors such as temperature and pH can affect an enzyme’s tertiary structure.
Use of modelling can be effective in the early stages of this topic, particularly in helping students to make links with previous learning on biological molecules. Models can also help students to appreciate the three dimensional complexity of tertiary structure rather than simple two-dimensional diagrams that are often found in textbooks, and help to explain theories such as lock and key and induced fit more clearly. Simulations can be useful in helping students to view dynamic processes such as collisions between substrate molecules and enzyme active sites.
In terms of practical work, there are probably more potential investigations to choose from than any other area of biology. Investigations can be carried out on any named factor that affects the rate of enzyme activity and can range from simple experiments to complex investigations that require a lot of preparation. Many investigations can be related to industrial contexts and simple analogues of industrial processes can sometimes be used in school/college science. When choosing practical investigations to conduct with your class, it is important to be clear as to the purpose – in some cases, you may wish to focus on developing their practical skills, in other cases you may wish to focus on linking theory to practice or interpreting and explaining data. Establishing a sequence, where you can help students to progress their skills and knowledge is key. For more advice, please refer to the Education Endowment Foundation’s guidance on practical work.
Enzymes delivery guide
A comprehensive delivery guide published by OCR, on the topic of enzymes. Although specific to the OCR A-Level specification, there is much content in here that is relevant for other level 3 qualifications. The delivery guide includes references to animations, video clips and practical activities, with a discussion on approaches to the teaching of this topic and dealing with common student misconceptions. There are also links to engaging nature articles which can be used for extension work and further reading – examples include articles on the inhibition of alcohol dehydrogenase and the functioning of lactate dehydrogenase in Antarctic fish
Modelling enzyme action
Although aimed at GCSE students, this collection of resources provides useful introductory ideas and activities that may serve as an initial recap. The stopmotion video clip using plasticine is a good example of how modelling can be used to help reinforce key ideas before more advanced concepts are dealt with. Students could be asked to do a similar but extended task whereby competitive and non-competitive inhibition are shown
ABPI Enzymes 16 +
From the ABPI website, this is a comprehensive set of notes and animations that explain enzyme structure and function. The animations and diagrams can be displayed full screen for use as a teaching tool but the website in general can be used by students to supplement their own notes and for revision purposes
Jelly Liquidiser
This short video would make an interesting start to an A level lesson on Enzymes. The video shows how pineapple, when added to a bowl of jelly is able to liquify the jelly, due to the enzyme action in the fruit which breaks down the gelatin in the jelly.
It would be possible to add in extra questions to the video to provide A level challenge, such as why does the pineapple have to be fresh? Why couldn't tinned pineapple be used? What enzyme does the Pineapple contain? When we say the gelatin is being broken down, what do we mean?
Students could quickly carry out this experiment using a) fresh pineapple, b) tinned pineapple and c) another fruit to compare and contrast the results and then write up an A Level standard explanation of what is happening
Enzyme-catalysed synthesis
In many enzyme-related practical activities, there is a tendency to focus on digestive enzymes. This can lead students to develop a misconception that enzymes only work to break chemicals apart. This practical investigation from the Nuffield Foundation offers an alternative enzyme reaction resulting in building up a new molecule. The investigation involves preparing an extract of potato tuber, removing starch from it and then checking for its ability to catalyse the synthesis of starch from different substrates.
Investigating the effect of pH on amylase activity
A classic investigation from the Nuffield Foundation, measuring the time taken for amylase to completely break down starch. A full experimental protocol is provided and the base experiment could be extended to level 3 by using a colorimeter to measure light transmission or absorbance of the starch and iodine solution
Investigating effect of temperature on the activity of lipase
A straightforward practical investigation that links understanding of biological molecules (structure of triglyceride fats) with enzymes. A full experimental protocol is provided, with simple qualitative judgments being used to gauge the progress of the reaction. Temperature is the variable that is being manipulated, but the investigation could be extended to look at the effects of changing other variables or introducing other factors (e.g. presence of bile salts)
Microscale investigations of catalase activity in plant extracts
Adapted with permission from Science and Plants for Schools, this is a microscale version of an investigation into the differing amounts of catalase found in different plant materials. This is a good introductory investigation to enzymes and can be extended to test representative tissues from other living organisms e.g. animal (liver) and fungi (mushroom). Inert substances such as sand can also be used and the concept of experimental controls discussed. The microscale nature of the investigation makes this much more manageable if resources or space is limited
Investigating an enzyme-controlled reaction: catalase and hydrogen peroxide concentration
A straightforward practical investigation which yields reliable results and can be modified to investigate the effect of various factors (e.g. temperature, substrate concentration, enzyme concentration) on the rate of an enzyme controlled reaction. This investigation protocol looks at the rate of oxygen production by the catalase in pureed potato as the concentration of hydrogen peroxide varies. The amount of oxygen can be collected either over water or using a syringe and a rate of reaction calculated.
Biology to technology
A biochemistry based activity from Oxford Sparks, this is a good exercise in comparing and contrasting different reaction pathways. Students are asked to consider why many industrial chemical reactions are being catalysed by enzymes and learn about the role of an important coenzyme, NADH. Students act in role as industrial chemists by evaluating the different ways of recycling NADH. The activity lends itself to group discussion and evaluative work and also links well with the topic of respiration.
Competitive and non-competitive enzyme inhibition
The concept of enzyme inhibition is often taught in a purely theoretical manner. This resource from Science & Plants for Schools (SAPS), enables students to investigate the effect of competitive and non-competitive inhibitors in a practical way on the enzyme beta-galactosidase and its degradation of ONPG (o-nitrophenyl beta-D-galactopyranoside). Using galactose (a competitive inhibitor) and iodine solution (a non-competitive inhibitor), students can investigate this aspect of enzyme controlled reactions in a practical and engaging manner
Enzymes Outside the Body *suitable for home teaching*
A useful comprehension exercise and material for wider reading, this Catalyst article explains how life would be too slow to exist without the assistance of enzymes. The article explores how enzymes work and their applications in various industries. It could be used as a pre-reading task before commencing the topic, as a recap from previous work or as stimulus materials for a wider research task
Investigating enzymes: inhibition of catechol oxidase in bananas
Bringing together both food science applications and theoretical understanding of enzyme inhibition, this is an excellent practical investigation that can be used to look at how inhibition of an enzyme can slow the rate at which fruit ripens. Students investigate how lead inhibits catechol oxidase, the enzyme responsible for turning fruit brown. This is a good activity for helping to consolidate theoretical understanding of inhibition and also for linking to real world applications.
Fruit Juice Production
A practical activity produced by Science and Plants for Schools (SAPS), this resource uses the context of fruit juice companies maximising their yield through the use of a variety of different enzymes (pectinases, amylases and cellulases) and treatments. Students are tasked with investigating the effectiveness of these enzymes in producing a clear and sweet fruit juice.
The protocol provided is straightforward for students to use and this would be an interesting investigation to add context to the topic of enzymes. It also provides a way in which previous study on the topic of biological molecules can be revisited with theoretical explanations for the observations that are made.
Testing the Viability of Yeast
Linking directly to the food industry, this investigation focuses on the autolysis (self-splitting) of yeast cells. Students are tasked with investigating the viability of yeast cells that have been exposed to varying degrees of salinity. Rather than relying on one simple test for viability, the investigation requires students to use both microbiological techniques (e.g. streaking of agar plates with yeast samples) and also biochemical tests (e.g. de-colouration of methylene blue) to gauge the activity of dehydrogenase enzymes.
The investigation will require some basic microbiological skills but would not be difficult for students with limited experience to complete. It would be a particularly good activity for bringing together a range of different skills, topics and contexts to help students think synoptically.
Nuffield Advanced Chemistry: Special Studies
Produced by Nuffield Advanced Chemistry, this is an excellent reference source for investigations and experiments that can be related to lab sciences, food science or metrology sciences with many of these featuring enzyme controlled reactions. The resources feature a comprehensive Student’s Book which features all the instructions for experiments, theories and questions. There is also a Teachers’ and Technicians’ Guide which provides technical information for setting up practical work with answers to questions about the experiments.
The resources would support any of the occupational areas within T-Level Science. It could be used to plan, revise or update existing schemes of learning and would be a worthy addition to any resource packs that are used by students or teaching staff.
Enzyme technology
A practical activity which looks at the technological applications of enzymes. Students are tasked with producing a bioreactor containing immobilised enzymes and using it to produce lactose reduced milk. The investigation involves the effect of varying temperature on the rate of an enzyme controlled reaction. The activity helps to provide a context to the work of food scientists and also links to earlier work that students will have completed on biological molecules.
Enzyme Activity in Fruits and Vegetables
This practical activity from Science & Plants for Schools (SAPS) provides materials that give a range of suggested activities for investigations into enzyme activity in ripening fruit. These include:
• the changes in enzyme activity during ripening and storage
• the activity of the same enzyme in different species
• the loss of an enzyme substrate (such as pectin or starch) during the ripening process
• the appearance of an enzyme product (such as glucose or galactose) during the ripening process
All of these are useful for students to understand the action of enzymes in situ. Small groups of students could be tasked with completing a different assay each and then be prepared to present their methodology, results and interpretation of the results to the rest of the class.