• Join over 1.2 million students every month
  • Accelerate your learning by 29%
  • Unlimited access from just £6.99 per month
Page
  1. 1
    1
  2. 2
    2
  3. 3
    3
  4. 4
    4
  5. 5
    5
  6. 6
    6
  7. 7
    7
  8. 8
    8
  9. 9
    9
  10. 10
    10
  11. 11
    11
  12. 12
    12
  13. 13
    13
  14. 14
    14
  15. 15
    15
  16. 16
    16

How are Potatoes CellsAffected by Osmosis?

Extracts from this document...

Introduction

How are Potatoes Cells Affected by Osmosis? Biology Coursework Osmosis in Plant Cells Aim: The aim of this experiment is to investigate the process of osmosis in plant cells taken from potatoes and to observe what changes which take place in the potato when left in varying glucose solutions. Background: The porous nature of the cell membrane means that only those molecules that are small enough will diffuse through it unimpeded. Larger molecules penetrate either slowly or not at all. Thus, the cell membrane is considered to be semi-permeable. In the diagram shown below, the cell has a higher concentration of glucose on the right-hand side compared to the left-hand side, as there are more glucose molecules per water molecules. Osmosis involves the passage of water molecules from a region of high water concentration (the left-hand side) to a region of lower water concentration (the right-hand side), through a semi-permeable membrane. This is why the water molecules will diffuse from the left-hand side, through the semi-permeable membrane and into the right-hand side. However, there will be no diffusion of glucose molecules across the semi-permeable membrane from the right to the left, as the glucose molecules are too large to pass. A solution consists of the molecules or ions of one substance (the solute) dissolved in another (the solvent). If a cell is surrounded by pure water, or a solution whose solute concentration is lower than that of the cell's contents, water flows into the cell by osmosis, and the cell swells up. In this case, the concentration of glucose in the left-hand side is lower than that of the right-hand side, and accordingly the solution is said to be hypotonic to the right-hand side. On the other hand, the right-hand side is said to be hypertonic to the left-hand side as the concentration of glucose is higher than the left. The following diagram further illustrates the act of osmosis and its effects on fluid levels in a beaker of solutions separated by a semi-permeable membrane. ...read more.

Middle

With this experiment, a knife was used to cut the potatoes. Care needs to be taken not to cut one's fingers during this step of the experiment. Actual Method: First, the 6 different 50 cm3 solutions were made consisting of 100% glucose, 80% glucose, 60% glucose 40% glucose, 20% glucose and 0% glucose (distilled water). The glucose solutions were made using the following table. ? The measuring cylinder was used to obtain the correct volume and therefore percentages of water and glucose for each glucose solution. The pipette was used to add water or glucose with precise accuracy, as required. Next, the solutions were poured into six labelled Petri dishes. 18 potato chips were cut out using the cork borer. Care was taken not to bore into the hole left by other samples which were taken from the potato. Every chip was full in diameter for the entire length of its cylindrical shape. The tile was used as a base for cutting the potatoes. All the chips were cut to exactly 50 mm using a ruler and a knife. The ends of every single chip were removed of its skin so that it would not affect the effects of osmosis. Three potato chips were placed into each of the six solutions and left for a period of twenty-four hours. Every Petri dish was covered and placed in way so that they all received the same amount of light (natural or un-natural), which might have affected the temperature of the Petri dish. Glucose Solution Length of Potato Chips Before Soaking (mm) x Length After Soaking # 1 (mm) # 2 (mm) # 3 (mm) Average Length [(#1)+(#2)+(#3)] 3 (mm) y Average Difference (mm) Percentage Change of Original 100(y - x) x 0% 50 55 54 55 54.7 4.7 9.3% 20% 50 50 53 53 52.0 2.0 4.0% 40% 50 49 49 49 49.0 -1.0 -2.0% 60% 50 46 46 45 45.7 -4.3 -8.7% 80% 50 45 45 46 45.3 -4.7 -9.3% 100% 50 44 43 ...read more.

Conclusion

Having taken so much care in setting up the experiment and keeping the variable to an absolute minimum, I feel that a fair test was give and that the accuracy of my results can be fully relied upon. Having used three potato chips for each solution, I increased the repetition of my experiment. Taking the average of the repeats would rule out any anomalous results that might have occurred due to any natural imperfections or irregularities in the potato chips themselves. If I had more time, I would have liked to do the experiment again so that I could record a wider range of data. I would have liked to record the mass of each potato chip before and after soaking in the solution. If I had performed the experiment at different temperatures, I could have observed how osmosis is affected by temperature. I would have also liked to use smaller intervals between the glucose solution concentrations, possibly 10% increments of concentrations of the solutions. I could have also used four or five potato chips per solution. This would have produced a much wider range of data and allowed me to have a stronger conclusion. Using different types of cells from various different sources would have provided an accurate account of how the effects of osmosis affect different types of organisms. When researching secondary sources, I came across an experiment in which osmosis was observed in human cells. Human red blood cells were placed in hypertonic, 1.2% salt solution and they were found to shrink perceptibly. If the cell was placed in a weaker (hypotonic) solution, they would swell and burst, a phenomenon known as haemolysis. Had I have had access to the proper equipment and facilities, I would have been especially interested to observe just how important it is to have an isotonic environment for living creatures. Overall, I am pleased with how the experiment turned out and I feel that I have gained a sound understanding of how osmosis occurs. ?? ?? ?? ?? - 1 - ...read more.

The above preview is unformatted text

This student written piece of work is one of many that can be found in our GCSE Life Processes & Cells section.

Found what you're looking for?

  • Start learning 29% faster today
  • 150,000+ documents available
  • Just £6.99 a month

Not the one? Search for your essay title...
  • Join over 1.2 million students every month
  • Accelerate your learning by 29%
  • Unlimited access from just £6.99 per month

See related essaysSee related essays

Related GCSE Life Processes & Cells essays

  1. Investigating the cellular water potential of potato cells.

    * Place 3 cylinders of potato onto one each of the five spikes, leaving a space between them all so that there is room for them to grow in size, making sure that it is obvious which potato samples is which.

  2. Osmosis is defined as 'the movement of water molecules from an area of high ...

    Evaluation The experiment was easy to do, but all the results I took had to be accurate. Unfortunately I had to change my plan several times. There are several reasons for this, these being that someone stole my boiling tubes, which I had spent 2 weeks getting exactly the right amount of salt into.

  1. How Does Osmosis Affect Plant Cells?

    24 hours in my case. I covered each beaker with cling-film to avoid any of the water leaving the beaker through evaporation (as this would make the solution more concentrated, through water loss) and to avoid anything entering the beaker and ruining the experiment.

  2. GCSE Biology CourseworkTHE EFFECTS OF GLUCOSE CONCENTRATION ON OSMOSIS IN POTATO CELLSPrepared by:Bhavin PatelTh...

    Temperature is a factor that affects osmosis. To avoid this to happen I will be using water bath and I will try to keep the temperature at a constant of 35 degrees. I decided to use the concentrations I am using in the main experiment after carrying out a preliminary study.

  1. Investigation Into How Osmosis In Potatoes Is Affected By Solution Concentration.

    The thin layer of cytoplasm surrounding the vacuole is what acts as the partially permeable membrane. When water enters the cell by osmosis, the cell swells up; however, the cellulose wall prevents it from bursting. The wall stretches, but does not break, and eventually the pressure inside the cell is

  2. In this experiment I intend to investigate the effects of osmosis on potato cells. ...

    Consequently, it is vital that the cell is able to accommodate some expansion. This is made possible by the support lent to it by the slightly elastic cellulose cell wall. It will support a turgid cell enough to prevent it from bursting (see left).

  • Over 160,000 pieces
    of student written work
  • Annotated by
    experienced teachers
  • Ideas and feedback to
    improve your own work