What Active Transport 'link' -

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

Introduction

| 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). what active transport

| 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 | | | Secondary | Indirect (Ion gradient) |

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. Some substances move passively, like rolling downhill