It is that important, marine fish even use osmosis to drink, and use their gills to excrete the salty water. Freshwater fish finds this process annoying though, because they give their water to the salty water to try and form an equilibrium they don’t want to form, and have to excrete high amounts of salty urine to stop the salt dehydrate the fish.
The biological problems with osmosis:
In plant root cells, if salt water was to get through the cell membrane, which could because of it similarity to water, it wouldn’t do great harm, but could do the opposite of water, and possibly dry the plant out, rather than let it have water.
Because the salt water contains salt solutions, which can’t get through the cell membrane, this could possibly make the salt water more concentrated than the root cells, and therefore let the plant start to give the salt water solution more water to equalise the solutions. This would dehydrate the plant, and make it shrivel up and go floppy, or FLACCID, and could kill the plant. (When the water enters the cell, the cell will swell up, and possibly rupture the cell membrane. It will go TURGID).
In humans, this also happens, but in a different way. We don’t necessarily lose a lot of water by direct osmosis of the skin, but if we drink it, it will dehydrate the tissues inside our body, and only then can the cells start to get seriously dehydrated.
Research source: www.infoplease.com/ce6/sci/A0860174.html
www.havapure.com/clean.html
My prediction
The outcome of this experiment will depend on the concentration of the salt solution. There will be a cut-off point of the concentration in the cell, which could mean two things. One outcome is that water will come out of the cell, because it’s the stronger solution, and will start to give the salt solution its water to make its contents equal. This means it will become smaller and dehydrated, or flaccid.
The other outcome is that water will go into the cell, because it’s the weaker solution, and will start to take the water given to it to make its contents equal. This could make the cell swell, and could rupture the cell membrane. It would go turgid.
Basically, if the concentration in the discs are less than 0.05 (the weakest concentrated solution), all of the discs will go turgid. If the concentration in the discs are more than 0.25 (the strongest concentrated solution), then the discs will all go flaccid. If the discs are between the two though, there will be a mixture of both. In other words, if discs go turgid, the mass will reduce (because water has left the disc), and if discs go flaccid, the mass will increase (because water will enter the disc).
The method
Concentrated solution (30ml each) Identical potato discs (0.6g each)
The main thing I need to do in this experiment is to test fairly. I will do this by using exactly the same weight of potato discs, and using exactly the same amount of concentrated solutions. In this case, I’m using 7 pieces of potato, each weighing 0.6g, and 7 x 30ml of concentrated solution. If I test fairly, this should mean that I wouldn’t need to check on the statistics I found on the discs as closely.
I will use 7 different concentrations, ranging from 0.05, up to 0.25, so I have a good range of statistics I can look at. From this, I may be able to see if I can find a set pattern between the relationship of concentration and the size of the discs.
Depending on the time we have for the experiment, I will probably spend longer setting the experiment up, as this experiment needs time to develop. This would mean that I wouldn’t need to wait another 3 or 4 days finding results if I repeat the experiment, for if I did something wrong the first time in setting the experiment up.
I will record the results in a table, so that they are easier to compare and contrast, and so that I can comment on my findings a lot easier. Because there are seven different results to compare, I don’t want to waste valuable time looking through paragraphs for data, which could be so easily found in a table.
Analysis
(Graph next page)
I think these are very wild results. I expected the results to be in a set pattern, but these results are all over the place, and in any other circumstances, would need to be done again to find some better results.
First of all, I would have expected all the discs’ weights to get lower and lower as the concentration got higher, because of the higher concentration making the cells give their water to the solution to dilute it. My line of best fit, which is drawn on the graph as well, isn’t roughly how I expected it to finish. Although it does tend to descend, I didn’t quite expect it to descend that sharply.
Conclusion:
I think we can’t draw much of a conclusion based on these results. These would need to be investigated much further before I could do a good conclusion, but I can say this. Because of the process of osmosis, the weight does go down when the concentration gets to 0.125 on the graph (on my line of best fit). This will be around about my cut-off point to where the discs go turgid, rather than go flaccid. Because the concentration of salt in the disc will suddenly be greater than in the solution, I think we can safely say that osmosis will allow water from the salt solution to enter the potato disc, rather than the opposite way around. Because of this, all the weights should stay below 0.6g, and therefore become flaccid. This can also support my prediction, because this happened (on the line of best fit).
Also, although the results before 0.175 weren’t in any set pattern, they never actually went below 0.6, and therefore with only one exception, which was 0.6g, they all did go flaccid. This supports my prediction as well, and does show there was indeed a set cut-off point between the flaccidity and turgidity between the concentrations in the discs.
Evaluation
Overall, as I have already hinted at, I think this experiment has gone wrong somewhere. All sorts could have happened to make the experiment to go wrong (see evaluation), but I don’t think anything could realistically have affected them this much. The results either go upwards as the concentration gets higher, as I’ve explained shouldn’t happen, or that the results take a very sharp decline, too steep to be realistically true. I think if the range of the concentrations were higher though, I think the results would gradually have matched my prediction. I say this because if you look at the last two results, they do follow my prediction, as the weights do gradually get smaller. This can only be another prediction though as far as this experiment is concerned.
This result will definitely not support my conclusion very well, because of the very strange results. They don’t follow any straight pattern that I can think of, and in fairness, I don’t think the experiment was done too well. We could have vastly improved it by been more careful with it, and taking more time with it. When it came to the experiment, the skin of the potato could have played a big part in the process. This could have affected how much it took or gave within the salt solution concentration, so we shouldn’t have left some skin on one or two of them if there was any on.
I did measure all the measurements exactly, so the only other factors I can think of are how much fluid was on the discs when we took them out of the concentrations, or, how much fluid was on the weighing scales if any excess water from earlier weight measurements was on them. This is especially true because were talking about tenths of a gram with this experiment.
One particular result that I thought that went wrong was the 0.15 and the 0.175 results. This is because the trend is that the weights gradually decrease as the concentrations get higher. These trends break the sequence, as they gain weight dramatically from the 0.125 weight, which in comparison, weighed just over half of the 0.175 weight, even though it is a higher concentration.
I personally don’t think the conclusion earlier on in the analysis of the experiment is enough to support or undermine my experiment, for the simple reason that the experiment has so many flaws as far as the wild results are concerned. Although there do seem to be some trends within the weights, these still don’t follow any exact trends, and we can’t say they would follow any strict pattern if range of the concentrations was greater.