Image by Chaozzy Lin

Movement of substances


  • Diffusion

  • Osmosis

  • Active transport

  • Concentration gradient

  • Water potential gradient

  • Molecules

  • Water molecules

  • Equilibrium

  • Net movement



Simple experiments

Simple osmosis and diffusion experiments allow students to observe the effects of the movement of substances. These experiments can be done in the classroom and can be done at the start or the middle of the topic. The rigor of the practical comes from the questions which force the students to connect theoretical knowledge with the reality of the observations in front of them.


Khan Academy: Advanced review of transport across a membrane

As with most Khan Academy lessons, this one is very thorough and covers some A level concepts. However, it is not too difficult for advanced students to comprehend and will help to flesh out their understanding of this important concept. The lesson covers passive and active transport, permeability, glomerular filtration, exocytosis and phagocytosis.

Biology Corner: Very simple diffusion quiz

Something fun for the kids to try when they have extra time. The accompanying lesson is also very easily digestible.


Red blood cells in a hypertonic solution

Elodea cells in a hypotonic environment

Elodea cells in a hypertonic environment

Learning Objectives:

  1. define diffusion and discuss its importance in nutrient uptake and gaseous exchange in plants and humans.

  2. define osmosis and discuss the effects of osmosis on plant and animal tissues.

  3. define active transport and discuss its importance as an energy-consuming process by which substances are transported against a concentration gradient, as in ion uptake by root hairs and uptake of glucose by cells in the villi. (Pure only)


Use the knowledge gained in this section in new situations or to solve related problems.