Biological molecules
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.
Proteins *suitable for home teaching*
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.
Unit O4: Large Molecules *suitable for home teaching*
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.
Lipids and Polysaccharides in Biology
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.
Quantitative Food Test: Protein Content of Powered Milk
This practical activity would complement work on biological molecules and provides a very useful activity for developing required mathematical skills. The practical requires the use of a colorimeter. If only one colorimeter is available, select one group to work with that and compare their results to those of other groups. Let each group acquire a set of results and then collate the class data to a spreadsheet visible to all.
The practical itself is relatively straightforward and should not present too much of a challenge for A level students. Using the results students should then be able to construct a calibration curve from which to estimate the concentration of protein in the known and unknown samples of milk powder.
Biological Molecules
The ABPI website has a topic entitled Chemistry of life. The pages within this topic provide a wealth of relevant material on biological molecules. Students could be directed to specific pages, such as page three for water or page five for carbohydrates. There are useful animations on some pages to illustrate particular reactions such as condensation and hydrolysis.
There are also activities on the website pages that students could be directed to , which would be suitable for both directed study or in class activities. For example, students are asked to produce an info graphic on the topic of carbohydrates (there are examples of other websites with info graphics).
Revision World
This is a clear and concise website which has all the detail required for A level biology. There are questions that can be answered at the end of sections.
The website could be given to students purely for revision. Alternatively they could be asked to evaluate the questions that are included and come up with three better questions to ask their peers. Groups of students could look at different sections and evaluate these against some criteria or questions. For example, is there anything missing? What could be added? Are all the terms used correct?