• 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

Isotonic Point of Potatoes

Extracts from this document...

Introduction

Aim: To determine the isotonic point of a potato. Research Question: To determine the isotonic point of a potato by placing it in different concentrations of salt (NaCl) solution and measuring the change in mass after a fixed time period. Background Information Osmosis is defined as the movement of water molecules from a region of low solute concentration, to a region of high solute concentration, through a semi permeable membrane, which is one that allows only certain small particles to pass through. A solution with a high water concentration, or low solute concentration is also called a hypotonic solution, and one with a low water concentration is known as a hypertonic solution. When a cell is placed inside a hypertonic solution, water molecules diffuse out of the cell (which has a higher water concentration, or is hypotonic) through the cell membrane, due to the high solute concentration outside the cell. This process is called exosmosis, and it makes the cell flaccid, as it loses water. The very theory can be applied to plants, which causes wilting. When a cell is placed in a hypotonic solution, water molecules diffuse from the solution into the cell, as the solvent concentration of the cell is lower. This causes the cell to become turgid, and it is called endosmosis. Source - http://biosimplicity.webs.com/ A solution which has the same concentration as that of the cell has no concentration gradient as both the cell and its environment have the same water potential. Thus the net movement of water is zero and the system is in equilibrium. Water molecules flow in and out at an equal rate by osmosis, causing the cell size to stay the same. ...read more.

Middle

thin * They had become very soft and completely flaccid * They could bend very easily and became very delicate, thus had to be held carefully * The colour had become very pale, and the cylinders appeared slightly translucent. * The cylinders seemed to be thinner from the centre. Table showing change in mass and percentage change in mass of the potato for each trial of the different concentrations Percentage change = (change in mass/mass before) * 100 Concentration of NaCl solution (M) Trial Mass before (?0.01g) Mass after (?0.01g) Change in mass(�0.02g) Percentage change in mass (%) 0.1 1 1.53 1.80 0.27 17.6 2 1.46 1.77 0.31 21.2 3 1.53 1.81 0.28 18.3 4 1.58 1.90 0.32 20.3 5 1.56 1.87 0.31 19.9 0.2 1 1.53 1.71 0.18 11.8 2 1.53 1.72 0.19 12.4 3 1.51 1.67 0.16 10.6 4 1.41 1.62 0.21 14.9 5 1.42 1.57 0.15 10.6 0.3 1 1.16 1.22 0.06 5.2 2 1.15 1.20 0.05 4.3 3 1.14 1.19 0.05 4.4 4 1.09 1.18 0.09 8.3 5 1.05 1.12 0.07 6.7 0.4 1 0.89 0.84 -0.05 -5.6 2 0.90 0.85 -0.05 -5.5 3 0.82 0.79 -0.03 -3.7 4 0.91 0.88 -0.03 -3.3 5 0.86 0.83 -0.03 -3.5 0.5 1 1.17 0.93 -0.24 -20.5 2 1.13 0.92 -0.21 -18.6 3 1.11 0.95 -0.16 -14.4 4 1.16 0.94 -0.22 -19.0 5 1.12 0.92 -0.20 -17.9 Calculation of average percentage change in mass of the potato Formula used: - Where x is the percentage change in mass; n is the number of trials and is the mean Concentration (M) Average or mean % change in mass 0.1 17.6+21.2+18.3+20.3+19.9/5 = 19.5 0.2 11.8+12.4+10.6+14.9+10.6/5 = 12.1 0.3 5.2+4.3+4.4+8.3+6.7/5 = 5.78 0.4 -5.6-5.5-3.7-3.3-3.5/5 = -4.32 0.5 -20.5-18.6-14.4-19.0-17.9/5 = -18.1 Table showing calculations for standard deviation: Concentration Trial % change in mass Deviation (d) ...read more.

Conclusion

* The temperature or pressure were simply monitored and not regulated, hence a change in temperature or pressure would result in a change in the rate of diffusion, which would in turn affect the final mass. * The surface area of the potato cylinders may not have been equal for all trials as the cork borer may have been pierced in the potato at different angles. * If the potato pieces were not completely dried before weighing then the mass of the residual water on the surface of the pieces (which had not diffused into the potato) would be taken into account. Consequently this would increase the mass of the potato, thus resulting in errors in the results. * Two different potatoes were used as the first potato was not enough to obtain 25 potato cylinders. As a result the isotonic points of both potatoes may have been slightly different. Improvements to the experiment: * The air conditioner and fans should have been switched off while taking readings of mass * Instead to keeping the beakers out, they could have been kept inside a fridge. This would prevent evaporation of water. The beakers could also have been covered with cling film to prevent evaporation of the water. This would ensure that the concentration of the solutions remained constant, and thus the rate of diffusion would not get affected. * In order to make the experiment more accurate, concentrations between 0.1M, 0.2M, 0.3M and 0.4M could have been taken, such as 0.15m, 0.25m etc. This would make it easier to find the exact isotonic point of the potato, and thus the experiment would have been much more accurate. * One potato should have been used in order to maintain a fair test ...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

Here's what a teacher thought of this essay

5 star(s)

"This is an extremely well written report that contains a high level of detail.
1. The background information is well researched.
2. The variables section contains a high level of detail.
3. The results have been well analysed.
4. The conclusion is complete.
5. The evaluation shows a good understanding of scientific processes.
6. The report is well structured.

Marked by teacher Luke Smithen 01/01/1970

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

    Biology Coursework - Osmosis

    5 star(s)

    Broken Glass - Broken glass is sharp and therefore dangerous. Do not place boiling tubes near to the edge of desks, make sure they are in test tube racks wherever possible. If a test tube is dropped, tell the teacher and clear it up as soon as possible.

  2. Marked by a teacher

    Investigate the effect of surface area on osmosis in potato tissue.

    4 star(s)

    I collected six sets of data, which was an adequate amount to show a pattern on the graph I produced. Although I would have expected the pieces of potato with a surface area of 48cm2 to have a mass difference double to that of 24cm2 because it is double the surface area, but my results did not show that.

  1. Marked by a teacher

    An Experiment to determine Water Potential in Potato Tissue.

    4 star(s)

    Also it gave me ideas about what kind of figures I was going to achieve in the real experiment and what concentration I should test potatoes on. Firstly I think using a normal pipette is not accurate enough therefore I'll use granulated pipette.

  2. Marked by a teacher

    "Osmosis" - The Potato Experiment.

    4 star(s)

    must be the same width length, because they must have the same surface area exposed to the solutions. This means that if one cylinder is exposed to more solution than another cylinder, then the one with the larger surface-area has a larger contact with the solution therefore the probability that

  1. Marked by a teacher

    Science Coursework: Investigating Osmosis in potato tissue

    4 star(s)

    Maybe we weighed and measured them wrong although that seems highly unlikely, yet for our next test we must make sure to weigh and measure the pieces of potato properly. Pre test #3 In this I will try to prove my prediction that the higher the concentration in the beaker

  2. The Effect of Glucose Concentration on Osmosis through Potato Tissue

    Different variety of potato have different concentration of water molecules in them, and also the cell walls can be different. This makes the experiment unreliable. - When the potato cords were taken out to be reweighed, they were placed on tissues, the tissues absorb the soak up some of the water.

  1. The effect of acid on the cell membrane

    After I decided to use Hydrochloric Acid, I did a second preliminary to explore the range of concentrations I should use. I prepared the following concentrations for the preliminary as follows: 1.0 molar HCl used 20cm� of 1M HCl, 0cm� water 0.8 molar HCl used 16cm� of 1M HCl, 4cm�

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

    for a plasmolysed cell. Minus 260 kPa is the suggested water potential, (for a quantity of 0.1 molar sucrose) for a maximum turgid cell. My potato tuber cell samples will be within these two amounts. This graph show that as the molarity increase the solute potential will increase.

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