Here's a breakdown:
* Assisted transport: This means the molecule needs help to cross the membrane. It can't simply diffuse across on its own.
* No energy expenditure: This means the process doesn't require the cell to use ATP (adenosine triphosphate), the cell's energy currency.
* Facilitated diffusion: This describes the process where a membrane protein helps a molecule move across the membrane down its concentration gradient (from high concentration to low concentration).
Key Points about Facilitated Diffusion:
* Passive transport: It doesn't require energy from the cell.
* Membrane proteins: Special proteins embedded in the cell membrane act as carriers or channels to facilitate movement.
* Concentration gradient: Movement is always from an area of high concentration to an area of low concentration.
* Specificity: Membrane proteins are specific to the molecules they transport.
Example: Glucose transport into red blood cells is an example of facilitated diffusion.
