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.