The effect of osmosis in potato cells with different concentrations of sucrose solution

The effect of osmosis in potato cells with different concentrations of sucrose solution

Aim: To test the effect of different concentrations of sucrose

solution to osmosis in a potato cells by putting potato pieces in test

tubes of water containing different concentrations of sucrose

solution.

Scientific Theory:

Osmosis is defined as the movement of water molecules across a

partially permeable membrane from a region of high water concentration

to a region of low water concentration. In a high concentration of

water the amount of solute (e.g. sugar) is low. This could be called a

weak or dilute solution. In a low concentration of water the amount of

solute (e.g. sucrose) is high. This could be called a strong or

concentrated solution. When two such solutions are divided by a

partially permeable membrane the water will move from the area of high

concentration to the area of low concentration, until both sides are

equal (have reached equilibrium).

Knowing that osmosis will occur across a partially permeable membrane

whenever there is a difference between the water concentrations on the

two sides of the membrane, and knowing that when this happens to cells

they will either become turgid if water flows into them, or flaccid if

water flows out of them, and thus change their volume, we want to test

the hypothesis that:

If the concentration of a solution into which a cylinder of potato is

placed is greater than a certain level the cylinder will contract, and

if the concentration is less than that level it will expand. The cell

membrane in cells is partially permeable and the vacuole contains a

sugar/salt solution. So when a cell is placed in distilled water (high

water concentration) water will move across the partially permeable

membrane into the cell (lower water concentration) by osmosis, making

the cell swell. This cell is now referred to as turgid. If done with

potato cells the cells would increase in volume and mass because of

the extra water. If these potato cells were placed in a solution with

a low water concentration, then the opposite would happen. Water would

move out of the cell into the solution. In extreme cases the cell

membrane breaks away from the cell wall and the cell is referred to as

flaccid. The potato cells will have decreased in volume and mass.

The greater the concentration of water in the so...

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example, with a carrot or an apple to see if osmosis affects them in

the same way as it does potato. I would also widen the range of sugar

concentrations to include 1.1M 2M. Moreover, I would like to see if

and when the cells reach a maximum and minimum weight.

Temperature could also be changed, for example the samples could be

placed in different test tubes at different temperatures to see if

temperature played its part in the osmosis of potatoes. 5 sets of 3

potatoes could be placed in test tubes at 10oC, 20oC, 30oC, 50oC and

60oC. Then leave them for 24 hours making sure all the variables in

the first experiment still apply however just using one molar

solution. Then after 24 hours re-weigh the samples and record the

result. I would expect that at high temperatures the potato samples

would gain the most weight. This is because at high temperatures the

water molecules would move faster and therefore equal the

concentration faster. A preliminary experiment could be set up

beforehand to find out how long the experiment should be kept going

because if the concentration of the potatoes equalises then the weight

of the potatoes will be almost exactly the same.