Difference between Diffusion and Osmosis
Diffusion and osmosis are two essential processes that have a lot to do with how molecules are transferred throughout the body. Both are distinctly different processes, although they are often interrelated as well. In this comparison article, we take a look at the key characteristics of both processes.
Definition
Diffusion is the random spreading of particles from areas with higher concentration to areas with lower concentration. The time period of this process depends on the diffusion equation. The concept behind diffusion is related to concentration gradient driven mass transfer, although diffusion may still occur even without the presence of a concentration gradient.
Osmosis refers to the movement of water molecules through a permeable membrane into a water potential gradient. This movement typically occurs from a region of high water potential or a low solute concentration, to a region with low water potential or a high solute concentration. This process occurs without the presence of energy, although it does eventually result in the release of energy, and can in fact be used to perform certain tasks. Just like diffusion, osmosis is also a passive process.
Process
Diffusion occurs mainly in substances in a gaseous state or in gas or liquid molecules. The molecules in these substances are constantly in motion and they collide with the membrane that would otherwise hinder their movement. The removal of the membrane causes the random mix of the gases or liquids in question.
Osmosis occurs when the medium surrounding the cells contain more water than the cell. This process then results in the cell gaining water. The process also results in the movement of important molecules and growth particles from one cell to another.
Comparison
The diffusion and osmosis processes actually have many similarities, although they have their differences as well. Both processes are means of molecular transport, although it is the nature of this transport that makes them different. While osmosis occurs with a semi-permeable membrane, diffusion does not require such a membrane to occur. Diffusion also involves the flowing of molecules from areas of higher concentration to areas of lower concentration. In the process of osmosis, this flow is reversed.
Diffusion also most commonly occurs between gas molecules, although it may also occur between solids and liquids or between liquids and gases. Osmosis on the other hand only occurs between two solvents.
Osmosis also takes much less time to occur than diffusion. In addition, diffusion occurs over relatively long distances, while the molecules move only short distances during osmosis.
As to their similarities, both osmosis and diffusion are considered means of passive transport. They also do not require external energy sources in order to bring about the process. Finally both osmosis and diffusion occur along the concentration gradient, and they may occur in living and non-living systems.
Similarities and Differences
Diffusion
- The random spreading of particles from areas with higher concentration to areas with lower concentration
- Occurs mainly in substances in a gaseous state or in gas or liquid molecules
- May occur in living and non-living systems
Osmosis
- The movement of water molecules through a permeable membrane into a water potential gradient
- Occurs when the medium surrounding the cells contain more water than the cell
- May occur in living and non-living systems
