Passive Transport
Passive transport is the movement of substances across a cell membrane without requiring the cell to expend energy. This movement is driven by the second law of thermodynamics, always moving towards equilibrium. Here are the key types of passive transport:
* Simple Diffusion: Movement of a substance from an area of high concentration to an area of low concentration.
* Facilitated Diffusion: Movement of a substance across a membrane with the help of a transport protein (carrier or channel).
* Osmosis: The movement of water across a semipermeable membrane from an area of high water concentration to an area of low water concentration.
* Filtration: The movement of water and small solutes across a membrane from an area of high pressure to an area of low pressure.
The Exception
The method of transport that is not passive is Active Transport.
Active Transport
Active transport requires the cell to expend energy (usually ATP) to move substances across a membrane. This is often necessary to move substances against their concentration gradient (from an area of low concentration to an area of high concentration).
Examples of Active Transport:
* The sodium-potassium pump, which moves sodium ions out of the cell and potassium ions into the cell.
* The uptake of glucose by intestinal cells.
Let me know if you'd like more detail on any of these types of transport!
