Comparing diffusion, osmosis and active transport
In animals, plants and microorganismMicroscopic (too small to see) organisms, such as bacteria and viruses, substances move into and out of cells by diffusionThe movement of molecules from an area of higher concentration to an area of lower concentration., osmosisThe 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 transportThe transport of molecules against their concentration gradient from a region of low concentration to a region of high concentration..
| Process | Description | Substances transported | Energy required |
| Diffusion | Substances move from a high to a lower concentration down a concentration gradient | Carbon dioxide, oxygen, water, food substances, wastes, eg urea | No |
| Osmosis | Water moves from a high to a lower concentration across a partially permeable membrane and down a concentration gradient | Water | No |
| Active transport | Substances more from low to higher concentration up 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 |
|---|---|
| Description | Substances move from a high to a lower concentration down a concentration gradient |
| Substances transported | Carbon dioxide, oxygen, water, food substances, wastes, eg urea |
| Energy required | No |
| Process | Osmosis |
|---|---|
| Description | Water moves from a high to a lower concentration across a partially permeable membrane and down a concentration gradient |
| Substances transported | Water |
| Energy required | No |
| Process | Active transport |
|---|---|
| Description | Substances more from low to higher concentration up a concentration gradient |
| Substances transported | Mineral ions into plant roots. Glucose from the gut into intestinal cells, from where it moves into the blood |
| Energy required | Yes |