Worksheets and lesson ideas to challenge students aged 11 to 16 to think hard about active transport, osmosis and diffusion (GCSE and Key Stage 3)
How do substances such as glucose, carbon dioxide and water get into cells? Cell transport is a fantastic area of biology that links together lots of different concepts, requiring synoptic thinking e.g. active transport requires an understanding of respiration, protein structure and concentration gradients. Start by asking students what substances move into and out of cells and then think about the problems that the cell must overcome. The membrane is made of lipid but water and oil do not mix so how does osmosis take place? Glucose is a massive molecule so how can it diffuse across a membrane made from tightly packed hydrocarbon chains?
GCSE practical to investigate how the rate of diffusion is affected by temperature. Students measure the rate of diffusion of food dye at different temperatures. Students also apply their understanding of diffusion and temperature to gas exchange in cold-water worms. (PDF)
Osmosis has some great practicals associated with it. Two of my favourites are the naked egg experiment and the gummy bears. For the naked egg experiment, place some uncooked eggs in vinegar overnight – this will remove the shell. Then place one egg in water and the other egg in a concentrated salt solution (8%) for 24 hours. Remove the eggs and observe what has happened. With the gummy bears (remember the theme tune!) just place them into different salt solutions and get students to observe what happens after 24hours. You can get them to take measurements before and after e.g. mass and length.
GCSE activity looking at how osmosis affects freshwater and marine organisms. Students work in small groups to apply their understanding of osmosis to explain different adaptations in marine and freshwater organisms. This activity requires students to have a good understanding of the principles of osmosis so they can apply their knowledge to new situations. (PDF)