Paper
Introduction
Knowing that osmosis (a diffusion of water) will occur across a semi-permeable membrane whenever there is a difference between the water concentrations on the two sides of the membrane, and knowing that when this happens to cells they will either become turgid if water flows into them, or plasmolysed if water flows out of them, and thus change their volume, we want to test the hypothesis that:
If the concentration of a solution into which a cylinder of potato is placed is greater than a certain level the cylinder will contract, and if the concentration is less than that level it will expand.
We have studied turgidity and plasmolysis in a textbook (Key Science-Biology, pages 143-144) and in a preliminary experiment, where we first added 2% sucrose solution to rhubarb epidermal cells, and saw them become plasmolysed, and then added water, and saw them become turgid. However, we did not use different solution concentrations, and did not measure the amount of contraction or expansion that took place. From our results in the main experiment, we should be able to work out not only the amount of contraction or expansion caused by each strength of solution, but also the concentration of the sap inside the cells.
Apparatus
For the experiment we will require:
Either cylinders of potato with a diameter of 6.5mm and a height of 5mm, or a potato, a borer with a diameter of 6.5mm and a scalpel. (To allow us to make our own).
Solutions of varying strengths (of sucrose and NaCl), or a solution of a known strength and distilled water. (To allow us to make our own).
Pins (To ensure that cylinders remain separate while in the solutions.)
Test-tubes
Callipers (To measure cylinder height and diameter.)
Diagram One of the test-tubes during the experiment. Three potato discs on a pin, not touching.
Method
We take a cylinder of potato, with a diameter of 6.5mm, from the potato, and cut it into separate cylinders each with a height of 5mm. We then thread at least three of the cylinders, to make the experiment fair (in case one of the cylinders is abnormal or damaged), on to a pin, keeping them apart from each other. We then make up solutions of either sucrose or sodium chloride, either by % strength or by molarity, and place 4 millilitres of each strength into a separate test-tube. We used a range of % sucrose solutions, going from distilled water (0%) to 2% (which we knew from earlier experiments would plasmolyse the cells), and a range of sodium chloride solutions from distilled water (0) to 0.4 molar (which would again be enough to plasmolyse the cells). We then place each of the sets of three cylinders on a pin into each of the different solutions, making sure that the cylinders are covered by the solution, and leave all of the test-tubes close to each other for 24 hours.
We assume that this means that the pressure and temperature in each case is the same, as these are factors which could affect osmosis, and we know that the volume, size and surface area of each cylinder is the same, and as they are all from the same potato, the only variable that we are altering is the concentration of the solution. Although ideally the experiment would be repeated several times, we were not able to do this as we did not have sufficient time.
After 24 hours we remove the cylinders from solution and, with callipers, which are more accurate than a ruler and would cover the likely range of sizes (from 4mm to 7mm), measure the new diameter and height of the cylinders. The results, in table and graph form are recorded below in the Results section.
Results
ConcentrationCylinder Diameter/mmCylinder Height/mmVolume/mm3 (2dp)Ave. Cylinder Volume/mm3
Pre-immersion6.56.56.5555165.92165.92165.92165.92
Sodium Chloride solution
0.0 Molar6.86.665.56.45.2199.74218.96147.03188.58
0.1 Molar66.56.84.44.94.9124.41162.6177.95154.99
0.2 Molar5.65.95.754.54.5123.15123.03114.83120.34
0.3 Molar66.15.94.94.94.5138.54143.2123.03134.92
0.4 Molar5.9655.65.45153.1152.6898.17134.65
Sucrose Solution
0%6.876.85.75.55.3207.01211.66192.48203.72
0.25%5.56555.55118.79155.5198.17124.16
0.50%55.255.56.65107.99140.1798.17115.44
1%5.554.95.95.15140.17100.1494.29111.53
2%4.44.64.44.85.24.472.9986.4266.975.44 Concentration of SolutionAverage % Change in Volume From Original
NaCl solution
0.0 Molar13.66
0.1 Molar-6.59
0.2 Molar-27.47
0.3 Molar-18.68
0.4 Molar-18.84 Concentration of SolutionAverage % Change in Volume from Original
Sucrose Solution
0%22.78
0.25%-25.17
0.50%-30.42
1%-32.78
2%-54.53
Analysis
The results show that, in accordance with our hypothesis, the cylinders will expand when external solute concentration is low (high water concentration), and contract in strong solutions (low water concentration). This is due to osmosis, where water passes from weak solutions to strong solutions across a semi-permeable membrane, such as a cell membrane. The graphs of % change against solution strength show that the results tend to form a curve, crossing the x axis (where there is no change in volume), at approximately 0.07 molar concentration for the sodium chloride solution, and at approximately 0.2 % for the sucrose solution. This concentration is the osmolar concentration (the total solute concentration) of the sap inside the cell. The volume change forms a curve when plotted against solute concentration because the cells, which have cellulose cell walls in addition to a cell membrane, will not expand or contract indefinitely, and will be held in shape within certain limits. However, the relatively low number of solutions tested (5) means that there is a range of possible values for the osmolar concentration of sap in the cell, and means that we cannot accurately predict values for volume change at different concentrations. To conclude, therefore, the results support our hypothesis, and we were also able to discover the approximate concentration of the sap in the cell.
Evaluation
Although the results of the sodium chloride and sucrose experiments support the hypothesis, there are several anomalous results and a large deviation for each result. These could be improved by altering the experiment, for example by keeping the test-tubes in a water bath at a set temperature, by keeping them at a constant pressure, and by measuring the sizes of potato cylinders before and after with a more accurate method, e.g. accurate weight measurement or volumetric displacement. The test might also be more accurate if the potato cylinders were left in the solutions for a longer period of time to allow the solution to penetrate fully to the core of the sample. The test could also be repeated more times for each concentration of solution, and with a greater number of concentrations, as this would decrease the error – a disadvantage of our experiment was that one anomalous result affected the others significantly (e.g. NaCl 0.2 molar concentration). Another factor is that the potato from which the cylinders are taken could be abnormal – this could be prevented by amalgamating sets of results, for example of a whole class, where each experimenter used a different potato.
Results that were not as I would have expected occurred with NaCl solution at 0.2 molar concentration (see above), where the range of results appeared too low. However, although this is apparently an anomalous result, it could have been caused by either experimental error – more significant when a small number of results are used, or a difference in the potato for those cylinders. Either of these would easily be recognised if a larger number of results were collected and used. Another result that appeared unusual was the ЎҐstepЎ¦ in the graph for the sucrose solution between 0.25% and 1% solutions – here different results for each cylinder pulled the average upwards by a noticeable amount, a problem that possibly would not occur if more measurements were taken.
For future experimentation we could repeat this experiment using a range of solution strengths very close to the value discovered here of sap osmolarity, to define more exactly its true value. We could also extend the experiment to use tissue samples from other plants, to discover whether the hypothesis is also correct for other tubers, and even for other plant tissues. We would then also be able to compare osmotic pressures inside different plants.
Другие работы по теме:
Investigation Of Nutrients Essay Research Paper October
Investigation Of Nutrients Essay, Research Paper October 14, 1998 Lab report INVESTIGATION 5: NUTRIENTS IN FOODS This experiment has to do with foods and their nutrients. We are finding out how much nutrients these 6 specific foods have and don’t have: cheese, hotdogs, egg yolk, egg white and potato. We are testing them for starch, sugar, fat and protein.
Tuber Cells Essay Research Paper DETERMINATION OF
Tuber Cells Essay, Research Paper DETERMINATION OF THE WATER POTENTIAL OF POTATO TUBER CELLS. Method. Five sucrose solutions with varying molarity and one control containing distilled water were prepared and poured into test tubes. The potato discs were dried, weighed and added to the test tubes. The discs were then weighed again after a period of 24 hours.
Osmosis Its A Bit Poo Essay Research
Paper Plan In my experiment, I plan to find out whether the concentration of sugar in water affects how much water will go in to a potato chip. I will do this by having twelve test tubes three with one molar of sugar solution, three with ? molar sugar solution, three with ? molar sugar solution and three with zero molar sugar solution.
Factors Affecting The Rate Of Osmosis Essay
, Research Paper `Planning Osmosis is the net movement of water molecules from a region of their higher concentration through a partially permeable membrane. This movement usually takes place through a
Osmosis In Tomatos Essay Research Paper This
Osmosis In Tomatos Essay, Research Paper This graph shown above gives the line of best fit for the percentage change in mass of the potato chips over the course of the thirty minute experiment. The graph is a curve that slopes downwards and does not go through the origin. Because the line is not straight and does not pass through the origin, it means that the percentage gain and loss in mass and concentration are not directly proportional.
Osmosis Lab Report Essay Research Paper Diffusion
Osmosis Lab Report Essay, Research Paper Diffusion is the movement of particles from an area of higher concentration to an area of lower concentration. Diffusion results because of the random movement of particles. The diffusion of water into and out of a selectively permeable membrane is called osmosis.
Irish Potato Famine Essay Research Paper One
Irish Potato Famine Essay, Research Paper One hundred fifty years ago in the late summer of 1845 one of the greatest human ecological disasters in the history of the world began in Ireland.
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.
The Membrane Essay Research Paper The MembraneThe
The Membrane Essay, Research Paper The Membrane The membrane has a double lipid layer through which fat- soluble substances will move, by passive transport or diffusion. The molecules will only move through if they are small enough.
The Potao Famine Gone But Not Forgotten
Essay, Research Paper A hundred and fifty years ago in September, 1845, the Dublin local paper “Dublin Evening Post”, reported a “disease in the potato crop”. This turned out to be the potato blight which destroyed 40% of the crop that year and almost 100% the next year. The devatation was known as “The Great Hunger” and resulted in wide spread starvation and mass emigration to Britain and the Americas.
BioReport Essay Research Paper 1 Cellular TransportaOsmosisOsmosis
Bio-Report Essay, Research Paper 1.) Cellular Transport a.Osmosis Osmosis is the diffusion of water molecules across a differentially permeable membrane from a region where water molecules are more concentrated to one where they are less concentrated. The transport of water is simple the cell being selectively permeable will allow water through it until an equilibrium is reached and at that time water will flow both in and out of the cell maintaining the equilibrium.
Diffusion And Osmosis Essay Research Paper 1
Diffusion And Osmosis Essay, Research Paper 1. a) Bulk movement is the overall movement of a fluid. The molecules all move in the same direction. Diffusion however is the random movement of
Osmosis Essay Research Paper The aim of
Osmosis Essay, Research Paper The aim of this experiment is to investigate the movement of water into and out of plant cells by osmosis. The cells chosen for study will be taken from potato tubers as they provide a ready supply of uniform material.
Gluclose Effects On Osmosis Essay Research Paper
Studying the Effect of Various Glucose Concentrations on Osmosis in a Potato Osmosis is the process in which water particles move from an area of high water concentration to an area of low water concentration through a semi-permeable membrane until the concentrations are equal.
Osmosis Essay Research Paper Title
Osmosis Essay, Research Paper Title: Osmosis in Potato Cells I am going to investigate: the diffusion of water by osmosis in plant cells, when changing the concentrations of sucrose in water, and measuring the change of mass of pieces of potato left in the solution for twelve hours.
Skinny Against Fat Essay Research Paper to
Skinny Against Fat! Essay, Research Paper to their being a couch potato. On the other hand, people who incorporate physical activity into their daily lives can be considered an exerciser.
Osmosis Lab Essay Research Paper Osmosis Lab
Osmosis Lab Essay, Research Paper Osmosis Lab Purpose The purpose of this lab is to determine the concentration of solutes inside of a potato s cell. We also want to know the composition of potato water and stuff . Also the scientific Phenomenon studied of diffusion/ Osmosis. Diffusion is the movement of molecules from an area of higher concentration to an area of lower concentration.
Potato Essay Research Paper The Andean Mountains
Potato Essay, Research Paper The Andean Mountains of South America is the birthplace of the “Irish” white potato that we eat today. European immigrants introduced potatoes to North America several times throughout the 1600s, but they were not widely grown for almost a century. Not until 1719, when Irish immigrants brought the potato to Londonderry, New Hampshire, were potatoes grown on a large scale.
Potato Famine Essay Research Paper In 1845
Potato Famine Essay, Research Paper In 1845, Ireland suffered through a potato famine that killed over two million Irish. History has taught us to believe that those two million died because of a fungus that caused all the potatoes to be bad. The guilt doesn’t rest with the fungus, but with the myriad of problems before it.
Study Of The Enviroment On The Cell
Membrane Essay, Research Paper Study Of The Enviroment On The Cell Membrane Dave Lima SBI OA1 Mr. Swanson 10/4/99 Purpose: To study the effect of environmental changes in the permeability of living beet root cells.
Potato Cores In Salt Solution Essay Research
Paper Scenario Plants in the soil have their roots in a dilute solution of mineral ions. When they are suddenly flooded with seawater, concentration of which is 0.3 molar Sodium Chloride, they are observed to wilt and become flaccid. Aim The aim of this experiment is to investigate the movement of water into and out of plant cells by osmosis.
Membrane Physiology Essay Research Paper IntroductionThe cell
Membrane Physiology Essay, Research Paper IntroductionThe cell membrane is a fluid structure that is made up of phospholipids and proteins. Its main function is to allow osmosis and diffusion to occur in a cell. It protects a cell from taking in molecules that are too large and other chemicals that are not permeable without energy being used.
Osmosis Essay Research Paper Osmosis1 IntroductionWe recently
Osmosis Essay, Research Paper Osmosis 1. Introduction We recently did an experiment on osmosis and it really helped me understand diffusion and osmosis much better. This experiment was really easy. We put the egg into three different types of liquids, vinegar, corn syrup, and water. My hypotheses for the egg in the vinegar was that the shell would be removed and dissolve.
Osmosis 2 Essay Research Paper Osmosis in
Osmosis 2 Essay, Research Paper Osmosis, in botany and chemistry, 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.
Mr Essay Research Paper An investigation into
Mr Essay, Research Paper An investigation into Hotel Users expectations of The Best Hotel Chain 1. Aims and Objectives 1. To examine what the expectations of hotel users are of The Best Hotel Chain.
Potatoes Essay Research Paper May 13 2001All
Potatoes Essay, Research Paper May 13, 2001 All the Pictures Potatoes. Instant potatoes at that. This was the meal of the evening. A plastic bowl half filled with a pasty hot goo that claimed to be somehow derived from a potato. Thoughtlessly, Jimmy gulped it down as he stared blankly at his computer screen.
Table Patterns Essay Research Paper Table Patterns
Table Patterns Essay, Research Paper Table Patterns Q1. For the first part of this investigation into table patterns I am going to see what happens when you add the two numbers in opposite corners of
Biology 2 Essay Research Paper BIOLOGY 2
Biology 2 Essay, Research Paper BIOLOGY 2 1. ORAGANELLES2. TYPES OF CELLS3. OSMOSIS/ DIFFUSION4. CELL THEORY 1. ORGANELLES small structures embedded in the cytoplasm e.g. plastids, vacuoles, mitochondria, lysosomes, centrosomes, endoplasmic reticulum (e.r.) 2. TYPES OF CELLS A.
Osmosis
Introduction: Osmosis is a net diffusion of water between two solutions that differ in solute concentration and that are separated by a selectively permeable membrane.