HypothesisI have done some preliminary work into osmosis in potato cells. 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 also tried different masses for the potato chips and came to the conclusion three grams would be adequate. If I had left them out in the open, then evaporation would have occurred, the amount of water would then be less that it should be, and as a result the controlled conditions of the experiment would have been compromised. This would make the potato hypersonic. When the pressure inside the cell becomes large enough, no additional water will accumulate in the cell even.
The thickness of the chip will already be the same, so I will cut the length of each chip to 3cm long. When water enters the cell by osmosis, the cell swells up; however, the cellulose wall prevents it from bursting. You can use potatoes to set up osmosis experiments for students of all ages and levels. In the experiment we shall use; 10% sucrose solution, 25% sucrose solution, distilled water, a potato and test tubes. When you place a potato chip in a salt or sugar solution, then if the potato has higher water potential some of the water will diffuse into the Sal solution which will cause the chip to lose weight. Under these conditions there will be a net movement of water into the cell. This causes a concentration gradient across the membrane which results in a net flow of water into the cell.
Through osmosis, sucrose from the potato moved along the concentration gradient out and into the test tube making the potato hypotonic. Graph the results Results Before put into solution Molecular concentration mole Weight of the potato grams 1 37. Then after 24 hours re-weigh the samples and record the result. Make four different solutions of sucrose: 10 percent, 5 percent, 1 percent and 0. Another way results could have been more accurate would be if each potato was cut into the same shape and size. If the membrane allows this ion through, the ions will move from the more concentrated side to the less concentrated side until reaching equilibrium. However with all this said I think that the experiment was successful and I was very pleased with the complete comparison of my results with my initial prediction.
However the water amount is in the salt solution is larger then the water will be diffused to the potato chip thus causing the chip to gain weight. Unit 4 Lab — Effects of Osmosis on Living Tissue Assignment Total: 35 Points Course Weight: 6 Pre-Lab Preparation - Review the following resources to complete this assignment: Textbook: Chapter 5, pg. When we did out preliminary experiment we only used 2%, 8%, 10% and distilled water. Initially the water potential outside the cell is 0 and is higher than the water potential inside the cell. It gets less steep as X axis gets bigger. The water potential of the potato would decrease because water moves from a high water potential region to a low potential region, and a dehydrated potato cell is hypertonic in comparison with the environment, forcing water to come into the cell.
In the first graph, the initial and final masses of the potatoes are shown and set side-by-side together in order to make an easier comparison between both values. This could be called a weak or dilute solution. Whilst doing the experiment we didn't dry the top pan balance before we measured the chips and we also forgot to dry the potato chips. Make one salt water solution, one sugar water solution, and for the third solution, simply use tap water. The effects of evaporation could affect the experiment by decreasing the amount of solution; I will combat this by putting a bung in the boiling tube to prevent evaporation taking place. In osmosis water moves through a selectively permeable membrane from a region of its higher concentration to a region of its lower concentration, and this shows the movement of water. For example new potatoes, King Edwards etc could be used.
A dialysis bag is filled with distilled water and then placed in a sucrose solution. I think this will happen because I expect a high amount of osmosis to be occuring in this situation, assuming that the solution is of higher water concentration than that inside the cell. This occurred when there was a 0. V Roberts Biology For You - Gareth Williams The Usborne Internet-Linked Science Encyclopaedia The Internet www. This would mean that the potatoes would have the same time contacting with the sugar solution. The one in the regular water looks like a nice white freshly cut piece of potato. Variables Description: Constant Variables These stay the same all the way through the experiment and are the fair test rules.
Remove the cylinders from the beakers and record the mass. The one in the salty solution will have shrunk, indicating that water is diffusing from a less concentrated solution to a more concentrated solution. Salt, Sugar and Pure Water This experiment helps students to differentiate between different degrees of concentration gradients. Variables Description: Independent Variables The independent variable is plotted on the x axis and is what you choose to change in the experiment. In the first experiment the gradient isn't steep as it should be. This liquid or hydrostatic pressure works against osmosis. This would make the potato hypotonic.
The purpose of the activities is to help you review material you have already studied in class or have read in your text. This is because in an experiment where the potato chip has a large surface area, there is a larger area of partially permeable membrane and therefore more opportunity for water particles to pass through. If there was one potato thicker than the other, then it may make a difference in how long it takes for the osmosis to occur. To determine the isotonic point of a sucrose solution and a potato 2. Diffusion is the result of this contact.
This means that the percentage gain and loss in weight and concentration are not directly proportional because the line is not straight and does not pass through the origin. I am going to use the concentrations 0M, 0. Scientificat is just a fun little blog run by a life explorer extraordinaire to keep track of her journeys while she learns more and more about this oddball world. Record the time at which the potato cylinders were added to the solution. Temperature:Temperature is one of the factors that affect osmosis, due to theexistence of more kinetic energy as temperature increases meaningmore effective collisions so we start by Using room temp to maintainVariable Reason? Some of the material will extend your knowledge beyond your classwork or textbook reading. The test tubes are then labeled accordingly, i. From the preliminary, we were trying to find out how osmosis actually occurred in potatoes, and gave us a vague idea on what the main experiment would be like.
After 20-30 minutes, remove the baggies from the water, and carefully blot dry and record the final weight. As well as the potato I could have found a more accurate way to measure out the solutions and to determine the molar concentrations. When solute concentrations are the same on both sides of the cell, there is no net water movement, and the cell is said to be in an isotonic environment. Fair test: To keep the test fair we need to keep the controls the same. This means that the solutions have the same concentration of solutes.