The net movement of molecules or ions from a region of a higher concentration to a lower concentration until their equally distributed and reached equilibrium
Passive process
Relies on inbuilt motion (kinetic energy) of diffusing molecules
Facilitated diffusion
Used for charged ions and polar molecules as they do not diffuse easily due to hydrophobic nature of fatty acid tails of phospholipids in membrane, therefore transported by facilitated diffusion via two proteins
Proteins used in facilitated diffusion
Channel proteins
Carrier proteins
Channel proteins
Form tubes filled with water enabling water soluble ions to dissolve through channel, but selective as channels only open in presence of certain ions when binded to protein whereas if a particular ion so present the channel is shut
Carrier proteins
Complementary shaped molecule binds to carrier protein causing a change in shape in way molecule is released to the inside of the membrane
