Passive Transport:
* Does NOT require direct energy input from the cell. It relies on the natural movement of molecules down their concentration gradient (from high concentration to low concentration).
* Examples: Simple diffusion, osmosis, facilitated diffusion.
Active Transport:
* Requires energy input from the cell. It moves molecules AGAINST their concentration gradient (from low concentration to high concentration).
* Energy source: Usually ATP (adenosine triphosphate), the cell's energy currency.
* Examples: Sodium-potassium pump, proton pump.
In summary:
* Passive transport is like rolling a ball downhill – it happens naturally.
* Active transport is like pushing a ball uphill – it requires effort (energy).
