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

Investigating the Factors affecting the water relations of plant cells.

Extracts from this document...


INVESTIGATING THE FACTORS AFFECTING THE WATER RELATIONS OF PLANT CELLS By Emily Akena INVESTIGATING THE FACTORS AFFECTING THE WATER RELATIONS OF PLANT CELLS Introduction This investigation studies the affect of different variables on the rate of osmosis in plant cells. The variables that would affect this investigation are: * Surface Area * Temperature * Concentration of surrounding solution * Concentration of solutes inside plant * Plant tissue - age, species, time of year The plant tissue to be used in this investigation is potato tuber tissue, because handling it is simple. The variable that will be investigated is the effect of concentration on the water relations of the potato cells as the concentration can be varied and measured accurately. Visual results can also be obtained. Temperature will not be varied, as it is hard to control and would therefore lead to inaccurate results. Temperatures that are too high will cause the proteins in the cell walls to be denatured and the plant to cook. The concentration of solutes inside the potato cannot be determined using school laboratory equipment, is uncontrollable and also varies. For each concentration to be investigated, I will measure the mass of the potato chip before and after it has been submerged in the solution and then calculate the percentage gain or loss of mass. Prediction Osmosis is the diffusion of water molecules from a higher to a lower concentration of water molecules through a partially permeable membrane. If there is a higher concentration of water molecules outside the cells, osmosis takes place into the cells through the partially permeable cell membrane to the large central vacuole. This increases the turgor pressure inside the cell and causes the cell to become turgid. ...read more.


If the percentage mass change is found, the resulting figures can be compared and plotted on to a graph. I will calculate the percentage change in mass using this formula: Mass after - Mass before x 100 = Percentage Mass Change Mass before * Repeat the experiment three times to produce a more accurate average value to plot onto the graph. Preliminary Results Concentration (M) Mass before (g) Mass after (g) Change in Mass (g) Percentage Change in Mass 0.0 2.21 2.41 0.2 8.3 0.25 2.33 1.94 -0.39 -16.7 0.5 2.22 1.55 -0.67 -30.2 0.75 2.04 1.38 -0.66 -32.4 1.0 2.36 1.83 -0.53 -27.54 Improvements From my preliminary experiment, I have decided to make the following changes. 1) To prevent excess water loss from the potato pieces, I will prepare the solutions before extracting the potato core. If this is not done, the potato will begin to dry out, therefore experiment results will not be accurate. 2) The potato pieces should be prepared, i.e. measuring and weighing in consistent order so that each piece spends the same amount of time in similar conditions. 3) As a 30cm3 measuring cylinder was not available and the next size of 50cm3 was too large for accurate measuring of the volumes I require, if the volume exceeds volume cylinder of 25cm3, I will measure the difference using a measuring syringe. I will also use a measuring cylinder as well as a measuring syringe to measure the salt solution. This is because the measuring syringe only has a maximum value of 10cm3, so multiple measurings for the larger volumes will decrease accuracy. This will increase the accuracy of measuring the salt solution and water. ...read more.


For example, around the potato eyes where shoots will grow, the concentration of solutes may be higher. This would increase osmosis into the cells. This variation could be improved by using smaller lengths of potato so all the samples could be obtained from a single potato core. Further inaccuracies could be caused by errors in measuring the water and salt solution. This would cause more or less osmosis to take place than would occur. This could be improved by using a burette to measure the liquids. Also the way in which the potatoes were dried after being submerged differed. Some may have been dried more thoroughly than others this would have caused results to be higher or lower than they otherwise would be. Also the excess water was not removed as the potato was cut. This problem could be improved by rolling the potato under a tile of certain mass. This way, the same force would be applied to each piece. There are no anomalous results obtained in the investigation. This evidence is not sufficient to draw a firm conclusion as more than five points are needed to draw an accurate best fit curve. More data is needed to support the curve. To provide additional data to determine that the shape of the graph and increase reliability, the experiment could be repeated but using concentrations of smaller intervals, for example testing concentrations of 0.125M, 0.25M, 0.375M, 0.5M, 0.625M, 0.75M, 0.875M, 1.0M. This would provide more points on which to base the line of my graph. Also, to prove the graph is correct, the isotonic point could be tested. By using, according to the graph, the isotonic point of 0.15M there should be no change in the mass of a potato piece. However, the isotonic point would vary from potato to potato, so the piece used to test the isotonic point should be from the same potato tuber. 2 ...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. Marked by a teacher

    To determine the water potential of a potato tuber cell using varying salt solution.

    5 star(s)

    I will also make sure they are all the same as the surface area is a variable that may distort the results. * Another thing that will be changed is the sucrose solution. The solution is a good environment for bacteria to grow and therefore made the preliminary experiment inaccurate.

  2. Aim To determine the water potential of a potato tuber cell

    Therefore one level of water potential may not be accurate for a potato tuba cell. Make sure that the area of which the cylinders are taken from are from the same area of the potato. This should ensure that within these cylinders there would be the same number of cells

  1. Estimate the concentration of the cytoplasm of potato cells.

    Length at End (cm) Change in Length (cm) 0.5 4.9 -0.1 0.25 4.9 -0.1 0.125 4.9 -0.1 0.06 5.1 +0.1 0.03 5.2 +0.2 0.015 5.3 +0.3 0 5.45 +0.45 Conclusion In my results I can see that from the concentrations of 0.5M to 0.125M the length of the chip decreases, and from 0.06M to 0M the length of

  2. Efeects of Osmosis in Plant Cells

    * Units of Measurement - moles/litre (m/l) * Cling Film (used as a seal) Diagram of My Preliminary Experiment Preliminary Experiment Method For my preliminary experiment I will prepare five visking tubing bags, which will each have 10ml of sucrose solution inside. The solution in each visking bag will have the same volume and concentration of sucrose.

  1. An Investigation of Factors Affecting the Rate of Osmosis.

    When the solution is higher in concentration than 0.27M then the potato should lose mass, because it has more water than the solution. To balance this out it goes into the solution. If the liquid that the potato is in has a solute concentration of 0.1; the potato has a solute concentration of 0.27.

  2. An Investigation to determine the Water potential of Potato cells.

    from www.coursework.info This greater surface area meant that at any one time, more of the potato cells in the cylinders could be in contact with the external solution and in the specified time more of the cells could be affected by the different concentrations of sucrose.

  1. To determine the water potential of potato tuber tissue

    I predict this to happen because of osmosis. If the two water potentials of two systems either side of a partially permeable membrane are the same, then there will be equilibrium and there will be no net movement of water molecules.

  2. Factors Affecting Osmosis In Plant Tissue

    The decision on what variable to change and what others to keep constant was the fact on whether the factor was discrete or continuous. This is because a quantitative prediction could only be made with the continuous factors, which would reach higher marks.

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