Here's why:
* Passive transport relies on the natural movement of molecules down their concentration gradient. This means molecules move from an area of high concentration to an area of low concentration, without the cell needing to provide energy.
Examples of passive transport include:
* Simple diffusion: Movement of molecules across a membrane from high to low concentration.
* Facilitated diffusion: Movement of molecules across a membrane with the help of transport proteins, but still down the concentration gradient.
* Osmosis: Movement of water across a semi-permeable membrane from an area of high water concentration to an area of low water concentration.
Active transport, on the other hand, requires the cell to expend energy (ATP) to move molecules against their concentration gradient (from low to high concentration).
