Study Of Osmosis By Potato Osmometer: Diagram, Experiment

Aim

To study by demonstrating the osmosis process by potato osmometer.

Theory

What is Osmosis?

Osmosis is the phenomenon whereby solvent molecules pass across a semipermeable membrane from a more concentrated region to a less concentrated region. It will carry on till the fluid quantity is equal on both sides of the membrane, thus balancing the fluid quantity on either side. The simple terms can be defined as osmosis diffusion of water from the high water potential region to the low water potential region. The osmosis potato experiment and study of osmosis by potato osmometer are the most frequent demonstrations of this phenomenon.

In Osmosis, What are Solvent and Solute?

The solvent is the fluid which moves through the semipermeable membrane and the solute refers to the dissolved particles which are present in the fluid.

Various Types of Solutions

Hypertonic Solution: Solution of high concentration of solute. When a living cell is placed in a hypertonic solution, water moves out of the cell because the water potential outside is lower than that in the cell, causing the cell to shrink and become plasmolyzed. This is demonstrated in the experiment potato osmometer.

Hypotonic Solution: A solution with a low solute concentration. When a cell is placed in a hypotonic solution, water enters the cell due to its higher water concentration outside, making the cell swell and become turgid. The potato osmoscope experiment shows this swelling effectively.

Isotonic Solution: A solution of equal concentration of solute and solvent on both sides of the membrane. Placing a cell in an isotonic solution results in no net movement of water, which allows the cell to retain its original shape. This balance can also be brought out using the potato osmoscope experiment.

The osmosis by potato osmoscope experiment is a very important method of showing the effects of different solutions and understanding the concept of osmosis in biological systems.

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Material Required

1. Fresh large-sized potato tuber

2. Sucrose solution of 20% concentration

3. Beaker

4. Water

5. Scalpel or blade

6. Petri dish

7. Bell pin needle marked with waterproof ink

Procedure

1. Cut the potato tuber into two halves using a scalpel or blade. Remove the skin and then cut these halves into square pieces.

2. Scoop out a small cavity from the mid-region of the potato tuber having a minimum thickness at the base. The cavity may be square or circular.

3. Fill half the cavity with freshly prepared 20% sucrose solution and put a pin into the cavity so that its mark coincides with the level of sucrose solution.

4. Place the potato osmometer in a petri dish or beaker containing water; the level is to be such that 75 % of the potato osmometer will be submerged in the water.

5. Allow to remain undisturbed for about 1 hour.

6. Observe and note the level of the sucrose solution in the osmometer at the end of the experiment.

7. Repeat the experiment with the cavity filled with water and the sucrose solution in the Petri dish or beaker.

Observation

After an appropriate length of time, the sugar solution inside the potato osmometer will rise and may also become coloured. This shows that on account of osmosis, the water moves inside the osmometer.

Conclusion

• In the potato osmometer experiment, there is an increase in the level of sucrose solution because of the movement of water into the solution through endosmosis.

• This process demonstrates the osmosis by potato osmoscope experiment whereby the water enters the sugar solution through the tissues of the potato and acts as a selectively permeable membrane.

• A water potential gradient is developed between the sucrose solution in the potato osmometer and external water in the beaker.

• The selectively permeable membrane of the potato tuber allows water to flow into the sugar solution, even though it is separated by a living potato cell.

• The result of this experiment illustrated that it can be used as a model for the theory of osmosis for a principle that shows how different water potential gradients can drive water movement.

• Osmosis in a potato demonstrates water dynamics in a biological system, and many experiments on osmosis use this potato experiment.

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