What is Facilitated Difussion?

Question

I need it in the simplest terms. Its for a science project.

Answer 1

Facilitated diffusion is the process by which certain solutes cross the cell membrane via transport proteins that span the bilayer. The solutes follow concentration gradients, and so, do not require additional energy (as by ATP). Glucose transport and bicarbonate-chloride exchange in red blood cells are classic examples of facilitated diffusion.

Answer 2

In cells, diffusion is the movement of molecules across the cell membrane. Molecules that are large can't cross the membrane easily, so they go through facilitated diffusion. In these cases, there is a protein that basically makes a tube that goes across the membrane, and molecules can use this tube to cross through instead of trying to squeeze between the phospholipids in the membrane. The protein helps, or "facilitates," the diffusion.

Answer 3

Facilitated diffusion (or facilitated transport) is a process of diffusion, a form of passive transport, where molecules diffuse across membranes, with the assistance of transport proteins.

Charged ions dissolve in water and diffuse through water channel proteins. These ion channels are gated so they can open and close, thus regulating the ion flow. Larger molecules diffuse through carrier proteins that change shape as the molecules are carried through, for example glucose and amino acid.

Small uncharged molecules can easily diffuse across cell membranes. However, due to the hydrophobic nature of the lipids that make up cell membranes, water-soluble molecules and ions cannot do so; instead, they are helped across by transport proteins. The transport protein involved is intrinsic, that is, it completely spans the membrane. It also has a binding site for the specific molecule such as glucose, or ion to be transported. After binding to the molecule, the protein changes shape and carries the molecule across the membrane, where it is released. The protein then returns to its original shape, to wait for more molecules to transport.

In contrast to active transport, facilitated diffusion does not require energy and carries molecules or ions down a concentration gradient.

Facilitated diffusion can take place in pores and gated channels. Pores never close, but gated channels open and close in response to stimuli.

The transport proteins participating in facilitated diffusion resemble enzymes. Just as enzymes are substrate specific and only catalyse certain substrates, transport proteins are solute specific and only transport certain solutes. Transport proteins also have a limit of how many solutes they can transport. Finally, molecules can inhibit the protein in a way similar to competitive inhibition in enzymes.

As an example of facilitated diffusion, glucose molecules diffuse by simple diffusion only very slowly across a cell membrane since glucose is not readily soluble in the phospholipid bilayer. However, glucose diffuses very quickly across a cell membrane by facilitated diffusion because the carrier proteins help the glucose molecule cross into the cell. Specific examples: GLUT1 in erythrocytes, a passive transporter involved in importing glucose molecules and GLUT2 in liver cells, involved in emporting glucose molecules.

Answer 4

This is a type of diffusion where proteins on the surface of the cell aid in moving charged or large molecules across the membrane that would otherwise be unable to. Glucose is the prime example.

Answer 5

It is a form of passive diffusion (requires no energy) in which proteins embedded in the membrane transport substances.