Transport Mechanisms

Passive transport mechanisms move substances down their concentration gradient without the use of cellular energy (ATP). This includes diffusion, osmosis, and facilitated diffusion.

• Diffusion: Movement of molecules from an area of higher concentration to one of lower concentration until equilibrium is reached.
• Osmosis: Diffusion of water across a selectively permeable membrane, crucial for maintaining cell turgor in plants.
• Facilitated Diffusion: Uses carrier proteins to move larger or polar molecules across the membrane without energy.

Active transport requires energy (usually ATP) to move substances against their concentration gradient. This is essential for maintaining concentration differences across membranes.

• Sodium-Potassium Pump: Moves sodium ions out of the cell and potassium ions into the cell, critical for nerve function.
• Endocytosis: Process by which the cell membrane engulfs extracellular material to bring it into the cell.
• Exocytosis: The reverse process of endocytosis, where materials are expelled from the cell.