move across bilayer from high to low concentration to reach equilibrium.
Facilitated Diffusion (Passive Transport)
dolecules will spontaneously flow "down hill" from a region of high concetration to low. they dont need no other driving force.
Protein mediated-carries bind to solute, channels form AQUEOUS pores (gated)
discriminate mainly on the basis of size and electric charge:if a channel is open, an ion or molecule that is small enough and carrie the appropriate charge an slip through a narrow trapdoor.
allows pasage only to those molecule or ions that fit into a binding site on the protein; it then transfer these molecules across the membrane one at a time by changing its own conformation, acting more like a turnstile than an open door.
bind solute on one side of and release the other requires concentration gradient, no net transfer
gate is controlled by the membrane potential. Major role in controlling signals to nerve cells,