Move substances against a concentration gradient using energy (ATP provided by Mitochondria).
- same as facilitated diffusion
- but energy is used
- A type of carrier proteins
- Conc. gradient of one molecule is used to move the other against its own conc. gradient
- e.g Sodium-glucose co-transport
1) Glucose moves into the intestinal epithelial cell with sodium via sodium-glucose co-transport protein.
2) Sodium removed by active transport in sodium-potassium pump - maintaining conc. gradient
3) Glucose then moves into blood by diffusion.