what is facilitated diffusion?

Answer 1

Solutes that are too polar or highly charged to diffuse through the lipid bilayer and are too big to diffuse through membrane channels can cross the plasma membrane by facilated difussion.In this process, a solute binds to a specific transporter on one side of the membrane and is released on the other side after the transporter undergoes a changhe in shape.

Like diffusion, facilitated diffusion is a passive process.The net result of facilitated diffusion is movement down a concentration gradient.The solute binds more often to the transporter on the side of the membrane with a higher concentration of solute.Once the concentration is the same on the both sides of the membrane,solute molecules bind to the transporter on the cystolic side and move out the extracellular side and move into the cytosol.The rate of facilitated diffusion(how quickly it occurs) is determined by the stepness of the concentration gradient across the membrane.

The number of transporters available in a plasma membrane places an upper limit,called the transport maximum,on the rate at which facilitated diffusion can occur.Once all the transporters are occupied, the transport maximum is reached, and further increase in the concentration gradient does not increase the rate of facilitated diffusion.Thus,much like a completely saturated sponge can absorb no more water,the process of facilitated diffusion exhibits saturation.

Hope this helps you.Please check my spelling too.I may misspelled some words.So many too typed.No time to check it.
(^^o)/

Answer 2

It is a type of diffusion where the movement of molecules downhill their gradient is helped by additional means, without requiring energy.

There are actually two cases (that I know of)

The first one is facilitated diffusion through cell membranes. In this case proteins (which can be carriers or channels) help the diffusing molecule to pass through the membrane. E.g. a sodium ion has usually lower concentration inside the cell so it would tend to diffuse into the cell. However it can't pass easily through the membrane because it is charged and the membrane is hydrophobic. Channel proteins create a hydrophilic tunnel which provides a path for Na+ to enter the cell.

Another type of facilitated diffusion occurs for the targeting of transcription factors (TFs) to specific DNA sites. According to the current model TFs diffuse freely until they encounter a part of a DNA molecule. Then they form non-specific interactions with it and scan the DNA molecule by successively releasing and binding again non-specifically DNA until they find their target site. This way they reach their target much faster than if they bounced off and diffused far away from DNA everytime the molecules collided at sites other than the two binding sites (one on the TF and the other being the target DNA site).

Answer 3

Facilitated diffusion is a passive process that involves a carrier protein.

Answer 4

It is a form of Active transport. Diffusion is the spread of a substance from a gradient of higher concentration to that of a lower concentration. Facilitated simply means that the diffusion is assisted or sped up

Answer 5

The first answer is WRONG. The second answer is correct.

It is a form of PASSIVE transport that goes through a carrier protein for an area of high to low concentration.

No energy required.