AP BIOLOGY

Detailed explanation-1: -In facilitated diffusion, molecules diffuse across the plasma membrane with assistance from membrane proteins, such as channels and carriers. A concentration gradient exists for these molecules, so they have the potential to diffuse into (or out of) the cell by moving down it.

Detailed explanation-2: -Facilitated Diffusion Requires Membrane Carrier Proteins Facilitated diffusion is also calledcarrier-mediated diffusion because a substance transported in this manner diffuses through the membrane with the help of a specific carrier protein. That is, the carrierfacilitates diffusion of the substance to the other side.

Detailed explanation-3: -In facilitated diffusion, substances move into or out of cells down their concentration gradient through protein channels in the cell membrane. Simple diffusion and facilitated diffusion are similar in that both involve movement down the concentration gradient.

Detailed explanation-4: -Facilitated diffusion is a form of passive transport and, therefore, the direction of transport is always down a concentration gradient.

Detailed explanation-5: -Facilitated diffusion uses channel proteins to move molecules across the membrane that could not directly diffusion through the phospholipid bilayer.