Transport //free\\ | What Active

| Feature | Active Transport | Passive Transport (Diffusion/Osmosis) | | :--- | :--- | :--- | | Direction | Low → High (against gradient) | High → Low (down gradient) | | Energy Required | Yes (ATP) | No | | Protein Carriers | Yes (pumps) | Maybe (channels or carriers for facilitated diffusion) | | Equilibrium | Creates or maintains disequilibrium | Reaches equilibrium |

is the movement of molecules or ions across a cell membrane against their concentration gradient (from an area of low concentration to an area of high concentration). Because this movement opposes the natural tendency of diffusion, it requires an input of chemical energy . what active transport

| Type | Energy Source | Mechanism | Example | | :--- | :--- | :--- | :--- | | | Direct (ATP) | Uses a pump that directly hydrolyzes ATP to move solutes. | Sodium-Potassium pump, Calcium pump (moves Ca2+ out of cytoplasm). | | Secondary | Indirect (Ion gradient) | Uses the energy stored in an ion gradient (created by primary transport) to drag another molecule along. | Symport (both move same direction) – Sodium-glucose symporter (Na+ flows down its gradient, pulling glucose against its gradient into the cell). | Feature | Active Transport | Passive Transport

In biology, cells must constantly move substances across their membranes to maintain life. Some substances move passively, like rolling downhill. However, cells often need to move substances in the opposite direction—from a low concentration to a high concentration. This process is called . Think of it as pushing a ball uphill; it requires energy. | Sodium-Potassium pump, Calcium pump (moves Ca2+ out

Antiport (move opposite directions) – Sodium-calcium exchanger. |

Introduction