Osmosis is a process by which molecules of a solvent moves through a selectively permeable membrane (a membrane that permits the passage of some molecules while inhibiting the way of others) from a less concentrated solution to an area where the solute concentration is higher. As a result of osmosis, the solute concentration on both sides of the membrane would be more or less equal. This equilibrium is vital for the effectual as well as optimal functioning of all cells.
A French clergyman and physicist named Jean-Antoine Nollet was the first to document the osmosis process sometime around 1748. Jean-Antoine Nollet was the first to document and explain this process, it was a French physician named René Joachim Henri Dutrochet who coined the term osmosis. The word osmosis is derived from the terms "exosomose" (movement of solute from within to outside) and "endosmose" (movement of solute from outside to within also known as reverse osmosis). A German chemist named Moritz Traube is credited with developing more sophisticated methods to measure flow of solute during osmosis. He developed the techniques in 1867.
As discussed above, osmosis is the process involving the passage of a gas or fluid through a semi porous membrane from a less concentrated solution to an area where the concentration of solute is higher. Aside from the external factors, the outcome of osmosis process will be equilibrium of solvents on both sides of the semi-porous membrane. This state, wherein the solvents are equally balanced on either sides of the membrane, is called "isotonic". Most commonly water used for demonstrating the osmosis process. But in reality, osmosis with various fluids and solutions is vital for the survival of every living organism from plants to humans on the Earth.
To understand the process of this phenomenon, it is important to know some key terms that are associated with osmosis. During osmosis, the fluid that goes through the permeable membrane is called a solvent and substance that dissolves in the fluid is known as solute. A solution is made up of both - the solute and solvent. A solution having low concentration of solute (a diluted solution) is said to be hypotonic. On the other hand, a solution with high concentration of solute is called hypertonic.
A typical example of this phenomenon is seen in plants. In fact, plants use this process to take up water and other nutrients from the soil they grow on. Usually, the solution present in the roots of the plants is hypertonic. Therefore, they absorb water from the hypotonic soil surrounding them. The membranes of the roots are selectively permeable, as they allow water and minerals needed by the plants for their survival to enter, while allowing the waste materials to go out. In fact, osmosis has a vital role in the cells of all plants and animals as it allows the fluids to enter and flow out of the cells walls. This way the cells obtain the nutrients necessary for them and exude the waste materials.
In osmosis, fluids pass into as well as outside the cells through the cell wall, which is a permeable membrane. However, normally the maximum flow of fluid is in one direction - either inwards or outwards, depending on the side of the permeable membrane having a higher level of solute. In other words, fluids pass from the hypotonic solution to the hypertonic solution. However, the flow of the fluid can be altered by enhancing pressure in the solution that is hypertonic. As the pressure becomes intense, it becomes difficult for the solvent in the hypotonic solution to go through the permeable membrane. In such a situation, an isotonic state cannot be achieved.
The principles that underscore the process of osmosis are very important to understand various different concepts. For instance, at times the fatal medical condition called water intoxication takes place when people drink large volumes of water in quick succession resulting in a dilution of water that gushes without restraint all through their bodies. As a result, the diluted solutions within the body can forces through the cell membranes owing to osmosis. This may result in the explosion of the cells, which expand to accommodate the excess water in the body. On the other hand, dehydration causes the cells in the body to shrink and eventually die as the water that is flowing freely inside the body becomes extremely concentrated with solutes, resulting in the water to drain out of the cells with to reach an isotonic state.
Cells in our body take up water from their surroundings by osmosis. When human beings drink water, the cells in their body soak up water in the same manner as the roots of plant do. When the level of waste products in the human cells goes up beyond a limit, they are let out due to the osmotic pressure. When the osmotic pressure created within and outside the cell walls - a semi permeable membrane, enhances, the cells take up water from the blood. The blood is a more diluted solution compared to the constituents of the cells.
Many people often wonder why sea water cannot be drunk. The answer to this is simple if you are aware of the principles of osmosis. When salt is added to the blood, it enhances the concentration of solute, thereby lowering the osmotic pressure created at the cell walls. In such a situation, the cells are unable to take up the water and, hence, they gradually become dehydrated. In fact, if an individual drinks seawater only, he/she would actually die due to thirst.
The process of osmosis is extremely vital for our kidneys. It is important to understand that not only the cells of our body depend on osmosis for survival and functioning, but osmosis is also crucial for different organs, such as the kidneys. Our kidneys are responsible for filtering the waste products present in the blood and subsequently excrete them from the body through urination. Each of the two bean-shaped kidneys comprises over a million micro filters known as nephrons. These neurons work to hold back the blood molecules, while they allow tiny particles like ions, glucose, and water to pass through after filtration. Once the filtration process is over, the kidneys absorb the water again to preserve a healthy equilibrium in the blood plasma. This entire process involves osmosis. In fact, the digestive system of human beings also depends heavily on osmosis process.
Osmosis, however, has two variations - for instance forward osmosis (when a solute passes through a porous barrier from a less concentrated solution to a high concentrated solution) and reverse osmosis (this occurs when the solute passes from a high concentrated solution to a less concentrated solution through a semi permeable barrier).
When water on one side of a porous barrier has impurities, pure water from the other side will flow on its own. But what makes water flow in the reverse direction? It has been found that even the contaminated water can pass through the porous barrier to the other side having pure water. However, in this case additional pressure needs to be created on the polluted water to prevail over the osmotic pressure. In fact, this phenomenon is known as reverse osmosis, which is the principle applied in the water filter systems.
When reverse osmosis is used in the water filtration systems it also has a few disadvantages. Besides being a slow process, reverse osmosis also does not completely remove or filter out hazardous impurities, which are equally small like the water molecules. Such contaminants include chlorine. Therefore, it is important that reverse osmosis in water filtration systems should always be used along with a carbon filter. In addition, reverse osmosis also lets out some minerals that are beneficial for our health. Hence, if the water filtering system at your house is using reverse osmosis it is recommended that you consume a lot of vegetables, fruits, greens and other foods that contain elevated levels of minerals.
On the other hand, forward osmosis is utilized to separate water from solutions that also contain other solutes. A higher osmotic pressure is applied on the solution to force the water pass through semi permeable membranes to make the "feed solution" (the solution having a lesser osmotic pressure) becomes more concentrated while the solution with high pressure dilutes. The solution which becomes diluted following the above process is subsequently used directly or sent through another operation for further processing. Most commonly forward osmosis is utilized for things such as desalination, water treatment as well as purifying water.
