The surface type of this phenomenon can occur by gliding, reptation, and leapfrog mechanisms.
The surface type of this phenomenon can occur by gliding, reptation, and leapfrog mechanisms. Molecules collide with walls more than each other in the Knudsen [NOOD-suhn] type of this phenomenon, whose namesake coefficient appears in Fick's first law. The rate of this process is inversely proportional to the square root of the molar mass of a gas according to Graham's law. Carrier proteins can transport sugars and amino acids in a facilitated process named for this phenomenon. For fluids through a membrane, this process is called osmosis. For 10 points, name this movement of substances from areas of high concentration to low concentration. 
The surface type of this phenomenon can occur by gliding, reptation, and leapfrog mechanisms.
diffusion (coefficient) [prompt on "effusion" or "osmosis"] 