Talking in simpler words, You can understand osmosis as the process in which makes the movement of solvent molecules in an out of the cell. This whole process is performed by the means of a selectively permeable membrane that we call as the plasma membrane.
What is Osmosis and Reverse Osmosis
Talking Behind The Definition:-
If we talk behind the definition, osmosis involves the movement of these solvent molecules through the plasma membrane from the region of high solute concentration to the region of low concentration so as to equalize the concentration on both the sides. Osmosis can be regarded as the main process that permits the entry and exit of water and other essentials in and out of the cell.
Talking About The Osmotic Pressure And Plasma Membrane:-
Talking about the osmotic pressure, it can be defined to be the minimum amount of desired pressure that you need to maintain an equilibrium with no net movement of solvent. It depends on the Molar concentration of the solute. You can take the plasma membrane to be a membrane that permits the entry and exit of the solute in and out of the cell from high concentration to low concentration. When a cell gets covered in water, the water molecules try to pass through the cell membrane and thus osmosis happens.
Examples of Osmosis:-
Talking about the body, the process will have been clear for you reading the first two points, but not let us discuss about the real life examples of it.
When a plant tries to get its nourishment from the soil, It makes its roots get deeper in the soil so as to quench its water needs. They simply concentrate the solutes in their root cells and the process of osmosis takes place permitting the water to reach the plant and thus the plant is able to fulfill its needs of water.
Purpose of Osmosis:-
Purpose of the process of osmosis for every type of cell, let it be the plant cell or even the animal cell is just to transport water and the other contents from one side to the other. Osmosis acts like a pump that does not permits the good and essential things to come in but also prevents the harmful things from coming in.
What Is Reverse Osmosis?
In this type of osmosis, the solvent is forced through the semi permeable membrane and pure solvent gets passed to the one side while the solute remains at the other side applying osmotic pressure from high concentration region to the low concentration region.
Take some raisins and simply keep them dipped in water for one night. You will see the next morning that the raisins have got hydrated with water and have got swollen up. This is an example of osmosis. If you have got a plant cell like that of an onion or an animal cell, you just need to keep it in sugar or salt solution and you will see that the process of osmosis is happening in this case as well but this case will depend on the type of solution in which the cell is kept like suppose the medium is hypotonic , the cell will gain water. If the solution is isotonic, there will be no net movement of water across the cell membrane and if the solution is hypertonic, the cell will lose water by osmosis.