Diffusion occurs through the process of random movement. We will see that, based on these random movements, particles demonstrate flux in a predictable direction. However, but this raises a tricky question: if movement is random, how can flux (net movement in a particular direction) occur? The key to understanding this apparent contradiction is the concentration gradient — namely, a difference in concentration of particles between two areas.
In this next section, we are going to introduce the idea of how random movement and gradients interact to produce a predictable level of flux.
photo credits: gradient |