Diffusion - Physiology

()Map TRANSPORT ACROSS MEMBRANES (Map)

Introduction

If gases or liquids are unevenly distributed over time this unequality is corrected by the movement of molecules from the region of high concentration to that of low. This is achieved by the process of diffusion. This works by the random thermal movement of molecules. If there is a gas present in an air tight room and then a door is opened into the next room there laws of probability state that some of the randomly moving molecules will escape through the door into the adjoining room and that eventually the concentrations in both rooms with be approximately the same. In the period between the foor opening and the rooms having the same concentratione net movement will be from the original room to the new room because as there are more molecules in the original room the probability of movement from here is increased.

Ficks Law

 Q = DA((C1 - C2) ÷ L)
 Q = the transport rate of a substance by diffusion 
 D = The diffusion coefficent 
 A = The cross sectional area which the substance is to diffuse accross 
 C1 C2 = The concentrations in the two areas  
 L = distance seperating the two areas