Introduction
It is a process where a fluid will transport itself through a semipermeable membrane, going from an area low in concentration of solute e.g. salt, to an area where the solute is a higher concentration. After this has taken place it ends with there being equal amounts of fluid on either side of the barrier that makes a state known as isotonic.
Plants have a strong and rigid cell wall that is on the outside of the cell membrane which is what stops the cell from opening when water is absorbed into it by osmosis. Osmosis causes the cell membrane to become even more rigid and inflated.
Osmosis in animal cells is where it will shrink and become crinkly due to any water that is leaving the cell continuously, and if it carries on entering
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The first test tube, contained pure distilled water, two to five had different concentrations and the sixth had pure Ribena. After the slices were put into the tubes they were left for 15 minutes and dried off with a paper towel and re-weighed. Both the weights recorded before and after were put into a table and the percentage of the weight differences was calculated and noted down.
Resources/apparatus
For this experiment, a range of equipment such as Ribena, uncooked potato chips, scalpel, beaker, distilled water, 2x teat pipettes, ruler, measuring cylinder, 6x test tube, test tube rack, lab coat, surgical gloves, a balance and a white tile was used.
Results
The results were put into a table showing how much distilled water each test tube contained, the weight of the uncooked potato slices before and after being added to the test tubes and the percentage that was worked out by X 100.
Potato Dilution Weight Before Weight After % of Change
1 0% 4.76 4.89 +2%
2 20% 5.32 5.22 -2%
3 40% 3.72 3.55 -5%
4 60% 3.05 2.88 -6%
5 80% 4.37 3.99 -9%
6 100% 3.14 3.23
The first thing I needed to see was how different concentrations affected the weight and length of the potato. So I needed to see each extreme - highest concentration and lowest concentration. I used 0 molar concentrations (the lowest) and 1 molar (the highest.) I then left each test for 20 minutes, but found after that time a slight reaction had taken place - the potato chips only increased or decreased by a very short amount. I then predicted that now I would have to leave the tests for a longer amount of time and use longer potato chips to ensure that there is enough of a reaction to compare
Conclusion In my conclusion, the potatoes with the lowest concentration gained the most mass, and would become hard relating back to the Turgor theory I stated earlier. In contrast to this, the potatoes in the most concentrated solution lost the most weight thus becoming plasmolysed and limp also relating back to the background I have mentioned earlier. Evaluation In general the experiment was succesful the results were consistent and also were in accordance with the theories made at the start.. The experiment could have been improved by: · More subjects used instead of potatoes · More potatoes · Wider time ranger · Different molarities Using this variety of methods could have improved the experiemnt, however I was generally satisfied with the results of this osmosis experiement.
In osmosis, water can travel in three different ways. If the molecules outside the cell are lower than the concentration in the cytosol, the solution is said to be hypotonic to the cytosol, in this process, water diffuses into the cell until equilibrium is established. If the molecules outside the cell are higher than the concentration in the cytosol, the solution is said to be hypertonic to the cytosol, in this process, water diffuses out of the cell until equilibrium exists. If the molecules outside and inside the cell are equal, the solution is said to be isotonic to the cytosol, in this process, water diffuses into and out of the cell at equal rates, causing no net movement of water. In osmosis the cell is selectively permeable, meaning that it only allows certain substances to be transferred into and out of the cell.
1:0 means that for every 1 cubic cm of distilled water we put in, we put in 0 cubic cm’s of solution. 1:1 means that for every 1 cubic cm of solution we put in, we added 1 cubic cm of distilled water. The solutions and the potato chips will be in boiling tubes in test tubes rack for safe storage. We will leave these for 24 hours. The next day when we would come to check them, after 24 hours, we would take the potato chips out of the boiling tubes to weigh them.
Osmosis is the facilitated diffusion of water across the cell membrane of a cell. The inside layer of the cell membrane is hydrophilic, meaning water cannot easily pass through the membrane. The cell membrane has to have aquaporins, which are water channel proteins, that move the water across the membrane. If there is a water and salt solution outside the cell, the salt can enter the cell by diffusion, but the cell membrane is not permeable to the water. Because there is more solute solution inside the cell, there is less water. The aquaporins move the water across the membrane until equilibrium is reached.
To investigate the osmotic effect of changing the concentration of sucrose solution; distilled water, 20% sucrose solution, 40% sucrose solution, 60% sucrose solution on the change in mass of potato cylinder after 30 minutes of being in solution.
Conclusions: There is a pattern on the graph, and data table, which shows that as the concentration of the sucrose solution increases, the potato's percentage change in mass decreases.
When I am not using them I will place them away from my experiment and
Investigating Osmosis In A Potato Introduction: "Osmosis is typically defines as the flow of one constituent of a solution through a membrane while the other constituents are blocked and unable to pass through the membrane. Experimentation is necessary to determine which membranes permit selective flow, or osmosis, because not all membranes act in this way. Many membranes allow all or none of the constituents of a solution to pass through; only a few allow a selective flow. In a classic demonstration of osmosis, a vertical tube containing a solution of sugar, with its lower end closed off by a semi-permeable membrane, is placed in a container of water. As the water passes through the membrane into the tube, the level of sugar solution in the tube visibly rises.
Determining the Concentration of the Cell Sap in Potato Storage Tissue Aim: To determine the concentration of the cell sap in potato storage tissue. By using Osmosis, determine what the sugar concentration of cell sap is. Prediction I predict that the potato segment in the distilled water will definitely gain in weight because the solution outside it has a much higher concentration of water then in the cell sap meaning Osmosis will occur and the potato segment take in water. I predict that 0.2M sugar solution will also gain weight because it still has quite a high concentration of water outside the potato. The potato in the 0.4M solution will gain weight but the potato in the 0.6M and 0.8M solutions will lose weight.
We then put the stopwatch on and left them for half an hour. After we weighed each potato tube and recorded our results. We did the experiment twice. We did this to make sure our results were correct. Preliminary method: We did everything the same as in our other experiment except we
water in the potato, then the water will go out of the potato and into
To test this, we set up two experiments. The first experiment we set up had three cups. In each cup a potato slice and a different liquid was put in. In the first cup was filled with distilled water. The second cup was filled with salt water and the third was left empty.
The experiment was quite reliable as I found out accurately the mass gained/lost through osmosis. However, due to the time constraints I couldn?t set up measures to ensure the temperature of each potato strip was the same and the surface area. Also I would have worn latex gloves to ensure that impurities would not go into the test tube while putting the potato strips in.
Prediction I think that when the potato is placed in distilled water the potato mass will increase. This is because water, has, if pure, a weaker concentration than the potato, and the water molecules move in through a partially permeable membrane by osmosis. If the potato is in a high concentration salt solution, the potato mass will decrease because the potato is less concentrated than the salt solution, and the water will move through the partially permeable membrane into the stronger solution. However, if the potato mass stays the same after the experiment, this means that the water/salt solution and the potato must be of equal concentration.