Mass Transport (AQA AS Biology): Revision Note

Mass transport

• Mass transport in living organisms can be defined as:

the efficient movement of substances over large distances, usually via specialised transport systems

• Mass transport allows the movement of materials from exchange surfaces to the parts of an organism where they are needed, e.g.:

  • oxygen is transported from the alveoli to the body cells

  • glucose is transported from the intestinal epithelium to the body cells

• Mass transport also allows waste materials to be transported back to exchange surfaces, e.g.:

  • carbon dioxide travels from the cells back to the alveoli

  • urea moves from the cells to the kidneys

• The circulatory system in animals and the vascular tissue in plants are specialised transport systems; they use pressure changes to force substances to move in the required direction

  • These specialised systems are needed in multicellular organisms because the distances between the exchange surfaces and the cells are very large

  • Diffusion alone would be too slow to supply the cells with everything they need