To investigate the effect of varying sucrose (sugar) concentration on potato cells and to find out the concentration of sucrose in the potato cells.

4. Mass of potato

5. Type of potato used

6. Concentration of sucrose

2. The surface area of the potato used will affect the test because the more surface area the potato that is in the solution the more sucrose it will be able to absorb because the more cells it will have to store it in (Also the bigger the surface area the quicker the rate of osmosis will be.)

5. The type of potato used will affect the result because some potatoes may be able to absorb more sucrose because the cells are different. This is because the different types of potato will have different levels of sucrose (sugar) in to begin with so they will be able to absorb more/lees of the sucrose.

If these variables were not controlled then the results we would get would be no good because it would not be a fair test.

Equipment List

We will be using the following equipment

Boiling tube

Potatoes chips

Potato cutter

Sucrose (0,0.1,0,2.0,3.0,4.0.5.0,6.0,7.0,8.0,9.0,1)

Scales

Knife

Test tube

Test tube holder

Pen

Sticky label

Method

A range of sugar solutions will be prepared with concentrations from 0 M to 1.0, in intervals of 0.2. Sections of a potato will be cut using a knife to equal lengths (this will be 4cm in length) this will keep the surface area constant and their mass measured.10 ml of each concentration of sugar will be placed in three test tubes and labelled. We will then weigh the potato section on some scales. To each test tube a cut piece of potato will be added. These will be left for 24hours to allow the osmosis to take place. Then the potato pieces will be removed, the surface solution removed using towels and weighed. Three readings are taken for each concentration in order to get an average. The results will then be added to our result table.

Prediction

The greater the concentrations of water in the external solution the greater the amount of water that enters the cell by osmosis. The smaller the concentration of waters in the external solution the greater the amount of water that leaves the cell.

However, there will be a point where the concentrations of water inside and outside the potato cells are equal (isotonic). At this point there will be no change in the length, volume and mass of the potato, as the net movement of water will be zero, no osmosis has occurred. I think that the amount of water/Sucrose gained for the cells will be.

0 = 2

0.1=1.8

0.2=1.6

0.3=1.4

0.4=1.2

0.5=1

0.6=0.9

0.7=0.6

0.8=0.5

0.9=0.3

=0.1

As you can see my prediction works on the theory that when the cell is in the higher concentrations of sucrose (0.6-0.7 molecules) the more movement of water there will be. I back this up with my background info that the water will move from the high concentration to the low concentration.

Results

Conclusion

In this test I did not get any weird (except the one at 0.6, -10) results they all seemed to fit in to the pattern that I suggested in my prediction. You can see at concentration above 0.2 M to 0.4 M there were no further water loss/gained in the potato suggesting that the balance between the potato and the solution are equal. After this the potato did not gain any more water instead it started to lose water.

Evaluation

The graph obtained in the results has a strong resemblance to prediction I made. This suggests that the experiment was fairly accurate. The accuracy of the investigation was adequate, however the concentrations were measured using a measuring cylinder and so may not have been accurate (we also had to rush them). Also when the potato was dried to remove surface liquid it was not necessarily done the same on each potato, a more accurate way of drying would improve the accuracy further. Although 3 repetitions of each concentration are sufficient, there was a possible anomalous result (circled on graph). This part of the investigation would need to be repeated Other investigations could include using different varieties of potato or different plant tissues e.g. carrot.

This would show us more of the higher to less concentration theory.