Potato Essay Research Paper Osmotic activity in

Potato Essay, Research Paper

Osmotic activity in potato cylinders Skill Area P: Planning

Aim: To investigate the effect of varying concentration of a certain sugar solution on the amount of osmotic activity between the solution and a potato cylinders.

Hypothesis: Osmosis is defined as the net movement of water or any other solutions molecules from a region in which they are highly concentrated to a region in which they are less concentrated. This movement must take place across a partially permeable membrane such as a cell wall, which lets smaller molecules such as water through but does not allow bigger molecules to pass through. The molecules will continue to diffuse until the area in which the molecules are found reaches a state of equilibrium, meaning that the molecules are randomly distributed throughout an object, with no area having a higher or lower concentration than any other. For this particular investigation I think that the lower the concentration of the sugar solution in the test tube the larger the mass of the potato will be. This is because the water molecules pass from a high concentration, i.e. in the water itself, to a low concentration, i.e. in the potato chip. Therefore, the chips in higher water concentrations will have a larger mass than in higher sugar concentrations. Plant cells always have a strong cell wall surrounding them. When they take up water by osmosis they start to swell, but the cell wall prevents them from bursting. Plant cells become “turgid” when they are put in dilute solutions. Turgid means swollen and hard. The pressure inside the cell rises and eventually the internal pressure of the cell is so high that no more water can enter the cell. This liquid or hydrostatic pressure works against osmosis. Turgidity is very important to plants because this is what makes the green parts of the plant “stand up” into the sunlight. When plant cells are placed in concentrated sugar solutions they lose water by osmosis and they become “flaccid.” This is the exact opposite of “turgid”. The contents of the potato cells shrinks and pulls away from the cell wall. These cells are said to be plasmolysed. When plant cells are placed in a solution, which has exactly the same osmotic strength as the cells, they are in a state between turgidity and flaccidity. We call this incipient plasmolysis. “Incipient” means, “about to be”.

Variables: Variables Non-Variables to be considered

1) Solution concentration Surface area

2) Solution volume

3) Duration of experiment

4) Temperature

5) Solution

6) Conditions which experiment is kept in To create a fair test certain aspects of the experiment will have to be kept the same whilst one key variable is changed. I have chosen to vary the concentration of the sugar solution. This will hopefully give me a varied set of results from which I hope to make a decent conclusion. If any of the non-variables below are not kept constant it would mean it would not be a fair test. For instance if one of the potato cylinders was 1cm longer the surface area of the chip would be larger and there would therefore be more space for osmosis to occur. Doing all the tests at one temperature will control the temperature, so it cannot effect the results, so i am going to carry out my experiment in a controlled environment. To keep the water potential of the potato initially will be kept the same by using the same type of potato, which have been treated in the same way, e.g. have all been cut without being washed and peeled. The mass of the potato is a dependent variable, and this means that it will be measured

throughout the experiment. I will measure the mass in grams. The potato cylinder will be measured before it is put in the solution, and after. This will allow us to see whether

osmosis has taken place, and to what extent.

The volume of the solution that the potato chips are kept in must be fair. The cylinders must be totally submerged in the solution, i will make sure the amount of solution will be kept the same to make it a fair test.

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Planned method: A range of sucrose sugar solutions will be prepared with concentrations 0 molar, 0.25 molar, 0.5 molar, 0.75 molar and 1 molar.

Sections of potato will be cut using a scalpel and will be measured using a ruler. This part of the preparation must be done very accurately as a change in the surface area may allow more or less osmosis to occur.

The mass of each chip will be measured as well so that more results can be obtained. Three chips will be placed in each test tube each time so that I can take an average for each tube.

I will use 10 ml of each concentration of sugar solution and once in the test tubes they each will be labelled.

The potato pieces will then be placed in the different test tubes and then left for 24 hours.

Then the potato pieces will be removed, the surface solution removed by gently blotting paper towels over surface at the same pressure to keep it a fair test and then they will be re-weighed.

Skill Area O: Obtaining evidence

Method:

1. Using a cork borer i cut cylinders out of the potato

2. Using a scalpel and ruler I cut the cylinders down to roughly the same size. I had to be very careful whilst cutting the potato as the scalpel is exceptionally sharp. I

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