To investigate osmosis in sugar solution using potato cells.

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Inderjit Maan        GCSE Biology Coursework        18/03/2002

                Mr Niklaus

Investigating Osmosis in a Potato Cylinder

Aim: To investigate osmosis in sugar solution using potato cells.

Prediction: To make my prediction, I am basing it on my background information and on my preliminary tests. I predict, the larger concentration of sucrose, will decrease the lengths of the potato cylinders. Osmosis ( a diffusion of water) will occur across a semi permeable membrane when there is a difference  between the water concentrations on the two sides of the membrane. Knowing this, water will flow through them making cells turgid or plasmolysed if water flows out of them and all this will change the volume. I also predict that the isotonic solution will be 0.3 molarity solution.

Background Information:  From the Oxford Biology book, and the encyclopaedia. This is the information I had obtained and also using the information from my preliminary test.

If the concentration is great then the potato cylinder will contract by shrivelling up and if the concentration is lower than that level, it will probably expand.

In the preliminary test, I saw the cells of the potato plasmolysed in the concentration alone and when the water was added the potato cells were slightly becoming turgid.

From the teacher: If the sugar molecules are on the outside of the cell and water, the water then can move in through the tiny gaps as the molecules are small.  If the cell is placed in a solution containing less water than it does, water moves out of the cell and it becomes flacid. If the cell is placed in a solution of equal concentration to it’s content’s, no movement occurs. This is an isotonic solution.

Preliminary Results:  This test was a brief experiment to allow me to make my prediction and also to find my accurate range for the actual experiment. There was no average as the range was a random choice.  This was the results table:

We chose the accurate range between 0.0M and 0.5M because the tables show that the solution 0.0M had increased the cylinders length by 1mm and the 0.5M solutions had decreased the potatoes length by 1mm. This graph behind this page shows the trends on the graph.

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The graph shows that the first concentration 0.0M shows that the concentration was too much water than concentration. The 10.0M showed that there was too much molars in the concentration as it was all sucrose. However the graph shows that the concentration should be investigated between the ranges of 0.0M and 0.5M.

Fair test:

Apparatus:

Safety:

Diagram:

1. Use the core borer to cut out the potato cylinders

2. Cut the cylinders down to the size ...

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