Osmosis in our Daily Life

Certain day to day activities in our lives are performed by us very often. We just do. We do not know the science behind these activities. But we still do it. Let us see a few examples. Let us also try to understand the science behind these activities.

When a glass of water is added with a red food colour, then the colour spreads the entire glass slowly. The entire glass will have red colour tinge. The red colour diffuses throughout water.

When we add a teaspoon of sugar in hot tea and stir it with a spoon, then the sugar diffuses through tea and make the tea taste sweet.

When cooking is done in the kitchen, the aroma of food cooked in the kitchen spread to the next room.

When we open a perfume bottle, its aroma starts spreading in the room instantly. This happens because the gas molecules in the perfume diffuse into the air and spread through the entire room.

In plants, carbon dioxide gas diffuses through the stomata of the leaves for photosynthesis. Oxygen gas diffuses out of the stomata and lenticels of the leaves during photosynthesis.

There are many other examples we may come across in our everyday life. In all the above examples we observe that there is movement of particles from higher concentration to lower concentration.  The process of diffusion does not require any external energy. Therefore diffusion is a passive transport and takes place in liquids and gases.

This process is dependent on the kinetic energy of the molecules. Liquid molecules and gaseous molecules are at random motion. They will be colliding against each other and will be having kinetic energy. When substances diffuse, the kinetic energy of the liquid and the gas molecules transfer their energy into other molecules to increase their kinetic energy. Hence this process is dependent on the kinetic energy of the molecules. The process of diffusion is completed when the state of stability or equilibrium is reached. 

Osmosis is a special example of diffusion. It is the diffusion of water molecules from a solution with a lower solute concentration to a higher solute concentration through a semipermeable membrane until an equilibrium condition is reached. This process can be operated only in the liquid medium. This process is also a passive transport as no external energy is required.

A few examples that can illustrate osmosis are as follows:

When raisins are immersed in water, they swell due to the movement of water into them (endosmosis) when the same raisins are immersed in the strong saturated sugar solution, they will show shrinkage due to loss of water into sugar solution (exosmosis).

We feel thirsty after eating salty food. Why? Salt is a solute. Our cells become concentrated with salt after we eat salty food. So our cells draw water in its direction. So we feel thirsty and we drink water to bring stability in our cells.

Meat, fish, vegetables are stored in salt and fruits are stored in sugar. Why? They are easily attacked by bacteria that contaminate them. If sugar and salt are used as preservatives, the solute concentration is higher than the concentration of cytoplasm of bacteria that contaminate the food. The microbes lose water and their metabolism will decrease. Therefore the microbes will die.

Absorption of water by alimentary canal from stomach, small intestine and colon is an example of osmosis. Salts and minerals from water are transferred through osmosis into the cells. Water flows through the plasma membrane of cells due to osmosis. Concentration of water, glucose and salt is maintained inside the body due to osmosis. Osmosis helps in preventing cell damage and helps in their maintenance.

Absorption of water by roots of the plants is an example of osmosis.  Roots of the plants absorb water and minerals from soil and transport it to various parts of the body. They use osmosis to maintain minerals and water equilibrium in their cells. There is lower concentration of water molecules in the roots than in the surrounding soil. The roots generate “pressure” to draw water and nutrients from the soil.  Plant roots function as a semipermeable membrane, allowing water to infiltrate the roots. The inside of the root contains minerals, sugars and salts dissolved in water. When water is available in the surrounding soil, osmosis causes it to flow through the root wall to its interior. As the plant absorbs water, pressure builds on the inside. The osmotic pressure brings water in balance with the pressure of the water already inside, keeping the plant from bursting.

When our body is immersed in water for a long time, our body look fluffy because water outside our body is less concentrated when compared to water present in our body. Therefore water outside the body is trying to achieve equilibrium with water present in the body through osmosis. Same idea applies when an animal or a person drowns and is soaked in water for a long time. Their bodies become extremely bloated, as osmosis will continue to happen until equilibrium is achieved.

Osmosis plays a vital role in human life. It helps in the proper functioning of the kidneys. Kidneys are able to recover water from the waste material of the body because of osmosis. Kidney dialysis is also an example of osmosis.

Osmosis plays a significant role in marine life. There are fresh water and salt water animals.  Freshwater fishes and other animals maintain fluid balance in their body through osmosis. Since the salt concentration in their body is higher than the surrounding water, they do not need to drink water. This is because water is spontaneously absorbed by the salt present in their body. The marine water animals and fishes are adapted to high saline ecosystem. Since, salt concentration of the water is higher than the fish, the excess salt in the surrounding water draws water from the body of the fish. This is how osmosis is regulated.

 When we are suffering from severe sore throat we are advised to gargle salt water. The cells and the tissues surrounding the throat will be swollen up because of excess of water when there is sore throat. The salt water has lower concentration of water molecules than the cells of our throat. So water molecules move from the swollen cells of the throat to the salt water and reduces the pain and swelling of the throat.

When we are suffering from Diarrhoea we are advised to drink electral and fresh fruit juices. Why? Electral and fresh fruit juices have salt and sugar in addition to water and fruit extracts. Our intestines would have lost water and there would be no water in the cells due to Diarrhoea. When Electral is taken it diffuses through the cells and revive the intestines and put them back into action.

The contact lenses have to be soaked in salt water instead of distilled water before wearing. Lenses soaked in salt water will keep the eyes moist whereas the lenses soaked in distilled water will dry our eyes and will be difficult to wear.

Osmosis plays a very important role in our daily life.