can someone explain me about Facilitated diffusion ???

Question

which one is right?
Facilitated diffusion of a molecule into a cell would be more rapid if

---the concentration of the molecule outside the cell increased
or.
---more ATP were used.

Answer 1

Diffusion is the transport of material across a membrane.
That can happen passively (down concentration gradients), or actively ("pumped" using energy, usually from ATP).

When the material being diffused requires a structure, usually a trans-membrane protein, in the biological membrane in order to pass through, that transport protein is said to "facilitate" the diffusion. This, facilitated diffusion is the transport of material across the membrane via transmembrane proteins.

In common usage, this expression is understood to mean passive facilitated diffusion. Glucose following concentration gradients across the red blood cell membrane is a classic example.

Answer 2

Facilitated diffusion does not require ATP. In facilitated diffusion, a molecule is being moved by a protein carrier DOWN the molecule's concentration gradient. In many instances the same carrier will move the molecule into the cell at one time, and then out of the cell at another time. So, your answer is the firt one.

Answer 3

When I teach this to my bio students, I tell them that facilitated diffusion is like walking through a door..if you can fit you can get through (laugh,laugh,laugh...) It is controlled by concentration gradients....things move through until a balance is reached.

Active transport is almost the same thing, except you have to "pay", like you do to get into a movie theater. Then what happens...all the people cram together in one room. It requires energy to build up those molecules against the concentration gradient. ATP is used to "pump" the molecule against the concentration gradient.

Facilitated diffusion doesn't use ATP, active transport does....