Here's why:
* Active transport moves substances against their concentration gradient, meaning from an area of lower concentration to an area of higher concentration. This movement requires energy, typically in the form of ATP (adenosine triphosphate).
* Passive transport, on the other hand, does not require energy. It relies on the natural movement of substances down their concentration gradient, from high concentration to low concentration.
Examples of active transport:
* Sodium-potassium pump: This pump moves sodium ions out of the cell and potassium ions into the cell, both against their concentration gradients. This process is vital for nerve impulse transmission and maintaining cell volume.
* Glucose transport: In some cases, glucose is transported into cells against its concentration gradient using active transport. This is important for maintaining glucose levels in the blood.
Key takeaway: Active transport requires energy input because it moves substances against their concentration gradient, while passive transport does not require energy and relies on the natural movement of substances down their gradient.
