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Endosmosis and exosmosis processes are two types of osmosis that are vastly used in explaining biological transport processes through complex systems. Both of these processes come under the broad category of Osmosis. When the solvent of a solution goes into a cell, it is called Endosmosis whereas, if the solvent comes out of the cell, it is called Exosmosis. Before we look into the differences between them, let us get clear with the concepts of Osmosis and Tonicity of solutions.
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Read Also: Difference between Diffusion and Osmosis
What is Osmosis?
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A spontaneous diffusion process in which the solvent passes through a semipermeable membrane from a low solute concentration region to a high solute concentration region to equalise the solute concentration on both sides is called osmosis.
Osmosis
Jean Antoine Nollet was the first discoverer of the osmosis process.
Semipermeable Membrane: Biological or synthetic membranes that allow the passage of only certain kinds of molecules or ions in a solution are called semi-permeable membranes.
For example, plant cytoplasm, egg membrane, raisin skin, and so on.
Tonicity of Solution
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Tonicity is the measurement process of a concentrated solution with respect to other solutions of various concentrations. Since osmotic movements of the solvent of a solution pass through a semipermeable membrane that depends on an osmotic gradient, tonicity is used to measure the concentration of solution both outside and inside. According to the concept of tonicity, there are three kinds of solutions.
- Hypotonic Solution- A solution that consists of low numbers of solutes and hence results in a lower concentration than other solutions present while the osmosis process happens is called a hypotonic solution.
Types of Solution according to Tonicity
- Hypertonic Solution- During osmosis, when a solution consists of high numbers of solutes and hence results in a greater concentration than other solutions, is called a hypertonic solution.
- Isotonic Solution- A solution with the same number of solutes as other solutions, resulting in the same amount of concentration, is called an isotonic solution.
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What is Endosmosis?
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When the process of osmosis causes the solvent of a solution to enter into a cell, it is called Endosmosis. In biology, if cells are kept into any kind of hypotonic solution, due to osmotic gradient, the molecules of that solvent (mostly water) pass through the cell membrane (cytoplasm) and make the cells look expanded with a huge amount of water pressure inside it. This is called endosmosis. The hypotonic solution has more water potential and less solute than the cytosol (liquid of a cell) present inside the cell.
Endosmosis
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Examples of Endosmosis
Some examples of endosmosis are:
- Swelling of Raisin: When dried grapes are placed into a hypotonic solution or normal water, they will swell. Due to having high water potential, water passes through the membrane of grapes and thus the endosmosis begins. It swells up and becomes extended raisins after 24 hrs or so.
Swelling of Raisins
- Plant water absorption- Using the endosmosis process, the root hairs of any plant absorb water from the soil and continue the endosmosis process through the xylem tissues present in its steam until the water reaches every part of the plant.
Read More: Homogeneous mixtures
What is Exosmosis?
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When the solvent of a solution comes out of a cell through the process of osmosis, it is called Exosmosis. If cells are kept in any hypertonic solution, due to an osmotic gradient, the molecules of the solvent come out of the cell and the cell shrinks. This process is called Exosmosis. The high water potential inside the cell causes Exosmosis.
Exosmosis
Examples of Exosmosis
Some examples of exosmosis are as follows.
- Shrinking of raisins: Sugar syrup is a hypertonic solution. If swollen raisins are kept in sugar syrup. Water comes out from the cell by exosmosis process and raisins start to shrink in size. Raisins get heavier in weight.
Raisins kept in Sugar Solution
- Egg in saltwater: Egg yolk is mainly made of protein and water, which is less hypertonic than syrup. The membrane of an egg is semipermeable because it is made of calcium carbonate. Saltwater is a hypertonic solution. If an egg is put into the solution, water starts to come out of the egg and the egg shrinks.
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Difference between Exosmosis and Endosmosis
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The differences between Exosmosis and Endosmosis is tabulated below.
| Parameters | Exosmosis | Endosmosis |
|---|---|---|
| Movement of solvent | The solvent comes out of the cell in exosmosis. | The solvent passes through the semipermeable membrane to enter inside the cell. |
| Type of solution needed | For exosmosis, a hypertonic solution is needed. | Endosmosis needs a hypotonic solution. |
| Solution concentration | In exosmosis, more solute and less solvent is present in the surrounding than the cell. | In endosmosis, less solute and more solvent is present surrounding the cell. |
| Osmotic gradient | Osmotic gradient works towards the outside of the cell. | Osmotic gradient works towards the inside of the cell. |
| Example | Some examples are shrunk raisins in sugar syrup, eggs in saltwater etc. | Some examples are swelled raisins, plants’ absorption of water from the soil. |
Things to Remember
- Endosmosis is the process where waters enter a cell through its membrane.
- Exosmosis is the process where water comes out of a cell through its membrane.
- Endosmosis happens when a cell is in a hypotonic solution.
- Exosmosis happens when a cell is in a hypertonic solution.
- Water potential is higher in the surrounding area during endosmosis.
- Water potential is less in the surrounding area during exosmosis.
- The skin of raisins, egg membranes, plant’s semipermeable membrane etc. are semipermeable membranes.
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Sample Questions
Ques. What is Endosmosis? [2 marks]
Ans: When the process of osmosis causes the solvent of a solution to enter into a cell, it is called Endosmosis. In biology, if cells are kept into any kind of hypotonic solution, due to osmotic gradient, the molecules of that solvent (mostly water) pass through the cell membrane (cytoplasm) and make the cells look expanded with a huge amount of water pressure inside it. This is called endosmosis. The hypotonic solution has more water potential and less solute than the cytosol (liquid of a cell) present inside the cell.
Ques. What is Exosmosis? [2 marks]
Ans: When the solvent of a solution comes out of a cell through the process of osmosis, it is called Exosmosis. If cells are kept in any hypertonic solution, due to an osmotic gradient, the molecules of the solvent come out of the cell and the cell shrinks. This process is called Exosmosis. The high water potential inside the cell causes Exosmosis.
Ques: Write any three important differences between solute and solvents. (3 marks)
Ans: The three important differences between solute and solvent are given in the following table.
| Solute | Solvent |
|---|---|
| A substance that is dissolved by a solvent is called the solute. | The substance that dissolves the solute is called the solvent. |
| Less in quantity | More in quantity |
| A solute may be solid, liquid, or gas | A solvent is generally liquid or sometimes gas |
Ques. Give one example of both endosmosis and exosmosis. [2 marks]
Ans: One example of endosmosis is the Plant’s absorption of water. It uses an endosmosis process to soak water from the soil. The root hairs of any plant start to absorb water through the xylem tissues present in its stem until the water reaches up to every part of a plant. An example of Exosmosis is when swollen raisins are kept in sugar syrup. Water comes out from the cell by the exosmosis process. raisins start to shrink in size and get heavier in weight.
Ques. What is an Osmotic gradient? What is water potential? [2 marks]
Ans: When the difference between two different concentrated solutions creates a direction through a semipermeable membrane which is actually used for measuring the percentage of concentration is called osmotic gradient. The potential energy per unit volume with respect to pure water is called the water potential. The water potential of a solution helps to identify the water’s tendency to move from one side to another.
Ques. What is a semipermeable membrane? Give 2 examples of it. [3 marks]
Ans:- A type of membrane which transports only a certain kind of molecules or ions of a solution depending on its nature are called Semi-Permeable membranes. Some examples of semipermeable membranes are the skin of raisins, egg membranes etc.
Ques: What is a solution? Enumerate any five properties of chemical solutions. (5 marks)
Ans: A solution is a mixture of solute and a solvent.
Following are the different properties of solutions.
Properties of solutions
- A solution is a homogeneous mixture of solute and solvent.
- The constituent particles in a solution cannot be seen by our naked eye.
- Solutions cannot scatter a beam of light passing through them.
- Solute particles cannot be separated by physical methods like filtration.
- Neither solute or solvent particles settle down even when left undisturbed. Solutions are stable at a particular temperature.
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Ques. Write down the definitions of hypotonic, hypertonic and isotonic solutions. [3 marks]
Ans: Hypotonic Solution- A solution of lower solute concentration than other solutions is called a hypotonic solution. Eg- Normal pure water.
Hypertonic Solution- A solution of higher solute concentration than other solutions is called a hypertonic solution. Eg- sugar syrup.
Isotonic Solution-A solution of the same solute concentration as other solutions is called an isotonic solution. Eg- Blood.
Ques. Write down the difference between exosmosis and endosmosis. [3 marks]
Ans:
| Exosmosis | Endosmosis |
|---|---|
| The solvent comes out of the cell in exosmosis. | The solvent passes through the semipermeable membrane to enter inside the cell. |
| For exosmosis, a hypertonic solution is needed. | Endosmosis needs a hypotonic solution. |
| In exosmosis, more solute and less solvent is present in the surrounding than the cell. | In endosmosis, less solute and more solvent is present surrounding the cell. |
| Osmotic gradient works towards the outside of the cell. | Osmotic gradient works towards the inside of the cell. |
| Some examples are shrunk raisins in sugar syrup, eggs in saltwater etc. | Some examples are swelled raisins, plants’ absorption of water from the soil. |
Ques: What is meant by a colloid? What are colloidal solutions? (2 marks)
Ans: Colloids are microscopic particles suspended in a solution. The size colloids range from 1-1000 nanometres (10-9 m). Solutions containing colloidal particles are called colloidal solutions. Some common colloidal solutions are aerosols, clouds, smoke, air dust, gels, emulsions, milk, etc.
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