Active transportSpec 1.15
Active transport is the movement of substances from a more dilute solution to a more concentrated solution, which is against a concentration gradient. It needs energy from respiration.
Active transport allows cells to take in substances they need even when they are in short supply outside the cell. For example, root hair cells take in mineral ions from the soil when the concentration of the ions is higher inside the cell than in the soil.
| What moves | Direction | Energy from respiration? | |
|---|---|---|---|
| Diffusion | Particles, such as oxygen and carbon dioxide | High to low concentration | No |
| Osmosis | Water only, through a partially permeable membrane | Dilute to concentrated solution | No |
| Active transport | Substances such as mineral ions | Low to high concentration, against the gradient | Yes |