Active Transport is the process by which substances are moved from a more dilute solution to a more concentrated solution.
This movement is against the concentration gradient, which is from an area of lower concentration to an area of higher concentration.
Energy from respiration is required for active transport.
Comparison with Diffusion
Diffusion involves the net movement of particles from an area of higher concentration to an area of lower concentration (down the concentration gradient).
Diffusion does not require energy, whereas active transport does.
Examples of Active Transport
In Animals
Human Small Intestine:
The small intestine lining cells engage in active transport to absorb nutrients.
The process occurs when the concentration of sugars like glucose in the lumen is lower than inside the cells.
Sugars are actively transported into cells, then into the bloodstream.
Cells have many mitochondria to supply the necessary energy.
In Plants
Root Hair Cells in Plants:
Active transport occurs to absorb ions such as magnesium from the soil, which is necessary for chlorophyll production.
The concentration of ions is lower in the soil than inside the root hair cells.
Ions are transported into the cells and then moved to the xylem vessels towards the leaf.
Root hair cells also have numerous mitochondria for energy provision.
Study Resources
Additional questions and exercises on active transport can be found in the revision workbook available through the provided link.