processed-9FEEC76E-F24B-4FE0-A2C6-014D21B0AAA5.jpeg

# Cell Transport Mechanisms This document describes different types of cell transport mechanisms. ## Primary Active Transport * **Example:** Sodium-potassium pump * **Process:** Each cycle exports 3 Na⁺ from the cell and imports 2 K⁺ into the cell. * **Function:** Maintains a concentration...

# Cell Transport Mechanisms This document describes different types of cell transport mechanisms. ## Primary Active Transport * **Example:** Sodium-potassium pump * **Process:** Each cycle exports 3 Na⁺ from the cell and imports 2 K⁺ into the cell. * **Function:** Maintains a concentration gradient (more Na⁺ outside, more K⁺ inside) crucial for electrically excitable cells (muscle and nerve cells). ## Secondary Active Transport * **Example:** Sodium-glucose transporter (SGLT) * **Mechanism:** Cotransport; the kinetic energy of one substance moving down its gradient provides the energy to move another substance. In this case, the sodium gradient powers the transport of glucose into the cell. * **Function:** Enables glucose uptake into cells. ## Vesicular Transport * **Function:** Enables cells to take up or release large quantities of substances. Vesicles transport substances in or out of cells in bulk. * **Types:** * **Endocytosis:** Movement of substances into the cell. * **Phagocytosis:** Moves solids into the cell. * **Pinocytosis:** Moves liquids into the cell. * **Receptor-mediated endocytosis:** Receptors on the cell membrane bind to specific molecules, bringing them into the cell; example: cholesterol transport from blood. * **Exocytosis:** Movement of substances out of the cell. * **Function:** Replaces sections of the membrane and facilitates secretion. ## Transcytosis * **Mechanism:** Endocytosis followed by exocytosis. * **Importance:** Particularly important for transporting large molecules (e.g., plasma proteins) across capillary walls when the molecules are too large to pass through channels.