Active transport is an energy-consuming process that transports molecules against their concentration gradient.
Cells often require molecules that are present inside the cell at higher concentrations than outside. These molecules cannot move into the cell by diffusion.
Active transport moves molecules from an area of low concentration to an area of high concentration.
This is the opposite direction to movement by diffusion!
Cells use active transport to absorb useful molecules:
- Root hair cells actively transport ions from the soil. This is important for water uptake in plants.
- Villi in the small intestine actively transport glucose from the gut. This maximises nutrient absorption from food.