Comparing diffusion, osmosis and active transport
In animals, plants and microorganisms, substances move into and out of cells by The movement of molecules from an area of higher concentration to an area of lower concentration., The movement of water molecules across a selectively permeable membrane from a region of higher water concentration to a region of lower water concentration. and active transport.
| Process | Descriptions | Substances moved | Energy required |
| Diffusion | Substances move from a high to a low concentration down a concentration gradient | Carbon dioxide, oxygen, water, food substances, wastes, eg urea | No |
| Osmosis | Water moves from a high to a low concentration across a partially permeable membrane and down a concentration gradient | Water | No |
| Active transport | Substances move against a concentration gradient | Mineral ions into plant roots, glucose from the gut into intestinal cells, from where it moves into the blood | Yes |
| Process | Diffusion |
|---|---|
| Descriptions | Substances move from a high to a low concentration down a concentration gradient |
| Substances moved | Carbon dioxide, oxygen, water, food substances, wastes, eg urea |
| Energy required | No |
| Process | Osmosis |
|---|---|
| Descriptions | Water moves from a high to a low concentration across a partially permeable membrane and down a concentration gradient |
| Substances moved | Water |
| Energy required | No |
| Process | Active transport |
|---|---|
| Descriptions | Substances move against a concentration gradient |
| Substances moved | Mineral ions into plant roots, glucose from the gut into intestinal cells, from where it moves into the blood |
| Energy required | Yes |
A gradient is a slope. The diagram below shows the direction of movement of particles by diffusion, osmosis and active transport on a concentration gradient.
