<span>The word 'diffusion' means free movement across distance, with or without the presence of a barrier. However, there is a phenomenon known as facilitated diffusion which occurs at the cellular level. The cell does not allow free radicals and other harmful substances to enter and harm the cell organs. This is possible due to the structure of the cell membrane. The structure is such that, it allows only certain things to pass in and out of the cell. One such activity that allows selective movement in and out of the cell is the process of facilitated diffusion.</span>
