Biological molecules is often the first topic in an A level biology scheme of work and one where a lack of knowledge and understanding will undermine future understanding. It is essential that students can recognise and explain how the structure of biological molecules is then related to properties and to the functions these molecules perform.
There are a number of possible misconceptions and examination errors in this topic. Students need to be very clear about the terms, such as the difference between condensation and hydrolysis. Students often forget that although the 3D structure of proteins is important to function, it is the primary structure, ie the sequence of amino acids, that determines the 3D shape in the first place.
The practical work in this topic is relatively straightforward and many of the tests will be familiar to students. However, they must appreciate the level of accuracy and detail that is required at A level compared to Key Stage Four. Practicals for testing the presence of biological molecules are favourite ones to be tested within written exams, with questions such as why must the Benedict’s reagent be heated still not answered well (despite this also being discussed at Key Stage Four).
Practical involving chromatography and colourimetery also provide examiners with a rich source of possible questions to test A level biologists understanding of key concepts and mathematical skills.
Teachers should also remember that water and inorganic ions have important roles as biological molecules (and are included in this topic), and that their functions are also related to their properties.
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 other 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.
Links and Resources
This resource provides a clear and succinct summary of the structure, function and importance of biological molecules.
It could be used in a variety of ways. It could simply be a revision sheet for students, or it could be given to students just before the start of this topic for them to read and add further details. The first lesson could then involve individual students presenting what they already know about a particular group such as carbohydrates, proteins or lipids. This would provide an excellent opportunity for the teacher (and other students) to confirm the level of knowledge and understanding at A level compared to Key Stage Four.
This issue of the Big Picture magazine focuses on proteins, in particular the role of different proteins within the body.
There is a lot of information within this resource. Using individual articles, or perhaps a few related articles, would be a good way to make use of this excellent resource.
This resource is aimed at much younger students, although the principle of the Benedict’s test does not change.
A level students could be shown this experimental procedure and asked to rewrite it in a suitable format for use in a commercial food testing laboratory.
This is a relatively old resource and, although the format is not particularly user friendly, there is some useful material within it for A level biology teachers to revise their own knowledge and possibly for students.
Much of the chemistry content is above the required standard for A level biology. However, the experiments and data provided on particular pages could be used to develop useful activities, particularly in terms of testing practical understanding by written examination.
Page 34 onwards is useful as a detailed recap of protein structure for teachers, or possibly for students. The standard Biuret test which follows is a good example of a written procedure and questions one and three based on this practical would provide stretch and challenge. Pages 45 and 73 (onwards) provide some useful data that could be used within exam type questions to test experimental knowledge and understanding.
The format and content make this resource suitable as a teacher only reference for those wishing to consolidate their understanding of this topic before delivering it to their A level students.