Transport: Active

Both substances move in the same direction (e.g., the SGLT1 transporter moving glucose and sodium into intestinal cells).

| Feature | Passive Transport | Active Transport | | :--- | :--- | :--- | | | None (kinetic energy) | ATP, light, or redox energy | | Direction | Down gradient (high → low) | Against gradient (low → high) | | Carrier proteins | Channel proteins or uniporters | Pumps, symporters, antiporters | | Equilibrium | Reaches equilibrium | Maintains steady-state disequilibrium | | Example | O₂ diffusion, water osmosis | Na⁺/K⁺ pump, glucose uptake in intestines | active transport

Active transport is essential for nearly every physiological function in the human body: Both substances move in the same direction (e