Substances move by Diffusion, Osmosis and Active Transport
- Life processes need gases or other dissolved substances to happen
- e.g. For photosynthesis to happen, carbon dioxide and water have to get into plant cells.
- e.g. For respiration to take place, glucose and oxygen both need to get into cells
- Waste substances need to move out of cells so the organism can get rid of them
- These substances move to where they need to be by diffusion, osmosis and active transport:
- Diffusion - where particles move from an area of high concentration to area of low concentration
- e.g. gases can diffuse through one another, like smell spreading through a room
- Alternatively, dissolved particles can diffuse in and out of cells through cell membranes
- Diffusion and osmosis both involve stuff moving from area of high concentration to area of low concentration.
- Sometimes substances need to move in the other direction - active transport
- In life processes, gases and dissolved substances have to move through some sort of exchange surface.
- The exchange surface structures have to allow enough of necessary substances to pass through
- Exchange surfaces and adapted to maximise effectiveness: