Active Transport

Real World Example

Imagine you're trying to carry a heavy suitcase up a steep flight of stairs. Just like you need to exert energy to move that suitcase against gravity, cells use energy to transport materials through their membranes against a concentration gradient. In this analogy, the stairs represent the cell membrane, the suitcase is the material being transported, and the energy you use to lift it mirrors the energy cells expend to move substances from areas of lower concentration to areas of higher concentration.