Exchange and transport mechanisms

For this topic, students must develop a clear understanding of the fundamental principles involved with movement and transport of substances. At level 3, this topic expands significantly beyond the content typically covered in most GCSE specifications and requires more detailed explanations of cell membrane structure and processes such as simple and facilitated diffusion – along with the factors that can affect the rate of these processes.

Understanding of osmosis and active transport is also a requirement for T-Level Science

Students may struggle to categorise the different forms of transport, confuse details of different processes and may harbour some misconceptions from previous study. Establishing some clear and logical ways of thinking e.g. grouping passive and active forms of transport into separate categories and comparing them is likely to aid recall and understanding.

As this topic deals with fundamental aspects of biology, it is important that students do understand the concepts well and can relate them to applied examples.

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.

A PhET animation from the University of Colorado, this provides a simple way of visualising the role of channel proteins in cell membranes. The animation has interactive tools which enable the concentration of a substance to be increased or reduced on either side of the membrane and for channels to be either open permanently (leakage channels) or gated. A graph can be displayed which shows the changing concentrations on either side of the membrane over time. The animation can be displayed full screen and used as a teaching tool or used by students in their own time to reinforce their understanding.

A PhET animation from the University of Colarado, this provides a way of carrying out virtual experiments involving diffusion. Particle movement is clearly displayed and various factors can be altered, including both mass, temperature, concentration and radius size of particles. The animation can be displayed full screen, making this both a useful teaching tool and also a means by which students can experiment for themselves to consolidate their understanding

From the Queensland University of Technology, this practical activity involves modelling a cell membrane using egg yolk and oil. This is a good hands-on activity for students and helps them to understand the concept of hydrophilic and hydrophobic components of cell membranes. A final activity involving pouring of iron filings through the membrane also helps to explain the formation of vesicles and endo/exocytosis.

This is a good modelling activity and helps students to learn about the fluid mosaic model of membrane structure. It would perhaps be best undertaken as a homework task with a follow up exhibition/ or presentation. As well as simply building a representation of a cell membrane using various materials, it would be most beneficial to ask students to critique the model and identify the features which are well represented by the model and those which are not.

Quality AssuredCategory:MathematicsPublisher:Core Maths

This is a mathematical research task, provided by CfBT Education Trust. Students are tasked with applying their knowledge and understanding of surface areas and volumes of cuboids to cells. This is an ideal task for embedding mathematical skills and also making connections between mathematical theory and real-life applied examples

A resource by the Nuffield Foundation, this provides a basic practical activity to investigate the effect of surface area to volume ratio of three agar cubes on exchange. A student worksheet and spreadsheet for results is provided. For level 3 investigations, students could be given the opportunity to cut more cubes of different sizes, or to devise a range of shapes that utilise the same volume of agar but have different surface areas. Calculation of surface areas and volumes of cubes, cuboids and cylinders provides a good way of developing mathematical skills

A set of animations by ABPI which detail active transport processes, including co-transport and endocytosis and exocytosis. The animations can be shown full screen and hence used as a teaching tool to help students visualise these processes.

From Nuffield Foundation, a classic experiment to show the impact of osmosis on cells. A single layer of plant cells is placed onto a microscope slide and either distilled water or sodium chloride solution is added. Osmosis will occur, resulting in either turgid or plasmolysed cells. This could be extended to look at the effect of such solutions on human blood smears (refer to the appropriate Health and Safety guidance on this) and crenation or lysis of red blood cells

From the Nuffield Foundation, an experiment that shows how blood cells are affected by changing concentrations of dissolved solutes in the surrounding liquid medium – either lysis or crenation will be observed. There is a fair amount of preparation for this as students will need to produce their own blood smears (health and safety guidance is provided in this resource but you should check the latest guidance). The preparation time is well worth it though as this does provide a memorable experience for students and helps them to understand why the internal conditions of the body need to be tightly regulated.

Quality AssuredCategory:SciencePublisher:Gatsby Science Enhancement Programme

This is a very quick and easy reminder for students of the processes of osmosis. There is no need for level 3 students to undertake the investigation, although it would be possible to extend it in a variety of ways.

This brief summary could be used at the start of this topic to confirm students' understanding of osmosis from Key Stage Four. It would be interesting to see how many students answer the question underneath the photograph of the potato chips correctly!