Diffusion vs Osmosis - Difference and Comparison

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	Diffusion	Osmosis
Water:	Doesn’t need water for movement.	Needs water for movement
What is it?:	Diffusion is a spontaneous movement of particles from an area of high concentration to an area of low concentration through a semi-permeable membrane.	Osmosis is the spontaneous net movement of water across a semipermeable membrane from a region of high solute concentration to a solution with a low solute concentration, down a solute concentration gradient.
Process:	Diffusion mainly occurs in gaseous state or within gas molecules and liquid molecules. The molecules of gases are in constant motion and collide with the membrane. If the membrane is removed the gases will mix because of random velocities.	It occurs when the medium surrounding the cell has a higher water concentration than the cell, the cell will gain water. At the same time, many important molecules, and particles for growth, also move from one cell to another.
Importance:	This way they can create energy and other important nutrients.	In animals, osmosis influences the distribution of nutrients and the release of metabolic waste products. In plants, osmosis is partially responsible for the absorption of soil water and for the elevation of the liquid to the leaves of the plant.

1 Definition of Diffusion and Osmosis
2 Process of Osmosis vs Process of Diffusion
3 Difference in Function of diffusion and osmosis
4 Different types of osmosis and diffusion
5 Related Articles
6 References

[edit] Definition of Diffusion and Osmosis

Osmosis is the result of diffusion across a semi-permeable membrane. If two solutions of different concentration are separated by a semi-permeable membrane then the solvent will tend to diffuse across the membrane from the less concentrated to the more concentrated solution. This process is called osmosis.

Semi-permeable membranes are very thin layers of material and these allow small molecules like Oxygen, water, Carbon Dioxide, Ammonia, Glucose, amino-acids, etc. to pass through. But they do not allow larger molecules like Sucrose, protein, etc. to pass through.

Diffusion is a spontaneous process in which the particles pass from higher concentration area to lower concentration area through a semi-permeable membrane. It is the statistical outcome of random motion. Diffusion increases entropy, decreasing Gibbs free energy, and is thermodynamically favorable. Diffusion operates according to the boundaries of the Second Law of Thermodynamics because it demonstrates nature's tendency to wind down, as evidenced by increasing entropy. Diffusion occurs when the system is not in equilibrium stage. The two differ in the process involved and the functions they serve.

[edit] Process of Osmosis vs Process of Diffusion

Diffusion is the spontaneous net movement of particles from an area of high concentration to an area of low concentration through a semi-permeable membrane. For example, diffusing molecules will move randomly between areas of high and low concentration but because there are more molecules in the high concentration region, more molecules will leave the high concentration region than the low concentration one. Therefore, there will be a net movement of molecules from high to low concentration. Initially, a concentration gradient leaves a smooth decrease in concentration from high to low which will form between the two regions. As time progresses, the gradient will grow increasingly shallow until the concentrations are equalized.

Diffusion is a spontaneous process. It is simply the statistical outcome of random motion. Diffusion increases entropy, decreasing Gibbs free energy, and therefore is thermodynamically favorable. Diffusion operates within the boundaries of the Second Law of Thermodynamics because it demonstrates nature's tendency to wind down, as evidenced by increasing entropy.

Osmosis is the result of diffusion of water across a semi-permeable membrane. For example, if the medium surrounding the cell has a higher water concentration than the cell, then the cell will gain water by osmosis. Water molecules are free to pass across the cell membrane in both directions. The overall result is that water enters the cell and the cell is likely to swell up. If the water concentration in the medium is exactly the same, then there will be no net movement of water across the cell membrane because, water crosses the cell membrane in both directions, but the amount coming in is the same as the amount going out, so there won’t be any overall movement of water. The cell will stay the same size.

If the medium has a lower concentration of water than the cell it will lose water by osmosis. Again, water crosses the cell membrane in both directions, but this time more water leaves the cell than enters it. Therefore the cell will shrink. The movement of solvent is from the less-concentrated (hypotonic) to the more-concentrated (hypertonic) solution, which tends to reduce the difference in concentration.

[edit] Difference in Function of diffusion and osmosis

While osmosis influences the distribution of nutrients and the release of metabolic waste products in animals; in plants, osmosis is partially responsible for the absorption of soil water and for the elevation of the liquid to the leaves of the plant.

Diffusion can occur through a cell membrane, and the membrane allows small molecules like water (H₂O), oxygen (O₂), carbon dioxide (CO₂), and others to pass through easily. Hence while osmosis helps the plants in absorbing water and other liquids, diffusion helps other molecules to pass through and hence both facilitate the photosynthesis process. Both processes help plants to create energy and other important nutrients.

[edit] Different types of osmosis and diffusion

The two types of Osmosis are:

Reverse Osmosis: it is the process of forcing a solvent from a region of high solute concentration through a membrane to a region of low solute concentration by applying a pressure in excess of the osmotic pressure.
Forward Osmosis: Forward Osmosis is an osmotic process that, like reverse osmosis, uses a semi-permeable membrane to effect separation of water from dissolved solutes.

The types of diffusion are:

Brownian motion, for example of a single particle in a solvent
Collective diffusion, the diffusion of a large number of (possibly interacting) particles
Effusion of a gas through small holes.
Electron diffusion, resulting in electric current
Facilitated diffusion, present in some organisms
Gaseous diffusion, used for isotope separation
Heat flow
Knudsen diffusion
Momentum diffusion, ex. the diffusion of the hydrodynamic velocity field
Osmosis is the diffusion of water through a cell membrane
Photon Diffusion
Reverse Diffusion
Self-diffusion
Surface diffusion