An unassisted type of diffusion where a particle or a substance moves from higher to lower concentration
Diffusion refers to the net movement of molecules from higher to lower concentration. Diffusion may be a simple diffusion or a facilitated diffusion. A simple diffusion is one in which that occurs unassisted. Facilitated diffusion in contrast is an assisted diffusion in a way that it requires a carrier molecule. For instance, nonpolar particles that are small enough can readily pass through the membrane pores of the cell membrane. Since it occurs without the aid of a carrier molecule the force that drives the movement of the particle or substance is the force of diffusion. Molecules that are able to pass through the cell membrane through simple diffusion are carbon dioxide, oxygen, and ethanol.1 These molecules are hydrophobic in nature and therefore can easily diffuse through the hydrophobic lipid bilayer of cell membrane. The movement of these molecules will continue between two areas as long there is a concentration gradient. A concentration gradient pertains to the difference of concentration between two areas.
Simple diffusion and osmosis is similar in a way that the net movement occurs from higher to lower concentrations. However, in osmosis, the net movement of water molecules across the cell membrane is the one that is monitored. A simple diffusion in particular pertains to the net movement of solutes.
- free diffusion
1 Nishiura, J. Simple diffusion. Retrieved from ://academic.brooklyn.cuny.edu/biology/bio4fv/page/simple.htm.