• 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
  17. 17
    17

How does the concentration of a sucrose solution affect the rate of Osmosis in Potato Cells?

Extracts from this document...

Introduction

Jennie Lace 10c How does the concentration of a sucrose solution affect the Rate of Osmosis in Potato Cells? PLAN I have chosen to investigate how the rate of osmosis taking place in potato cylinders varies when I change the concentration of the surrounding sucrose solution. I will vary the concentration of sucrose in the solution, and carry out various measurements on the potato cylinders before and after the experiment, to see what affect changing the concentration has had. I predict that with the lowest concentration of sucrose, the potato will increase in mass, because of water moving into the cells. The percentage increase will then get smaller each time I increase the concentration of sucrose in the solution. At some point, the mass of the potato will not increase, and will be the same as it was before (when there is no net flow of water particles in or out of the potato cells). After this, the mass of the potato will start to decrease as I keep on increasing the concentration of the sucrose solution. At some point the potato cylinders will lose all the water that they are able to, and the percentage mass loss will stop decreasing. This is what I expect the graph of my results to look like: Osmosis is the movement of water particles from a weak solution (a hypotonic solution) to a strong solution (a hypertonic solution. It happens through a selectively permeable membrane, and is a type of diffusion. In a potato, water particles travel through the cell membrane, which is a selectively permeable membrane. During osmosis in a plant cell, the water particles move through the cell membrane and into the large vacuole, where they are stored in a solution of sugars and salts. For this experiment, I will be using sucrose, which has large particles that cannot fit through the holes in the selectively permeable cell membrane, but water particles can fit through, as they are much smaller. ...read more.

Middle

Mass of potato before (g) Mass of potato after (g) Change in Mass (g) Change in mass (%) 0% 7.32 7.73 + 0.41 + 5.6% 5% 7.44 7.74 + 0.30 + 4.0% 10% 7.14 7.15 + 0.01 + 0.1% 15% 7.31 7.13 + 0.00 + 0.0% 20% 7.45 7.15 - 0.30 - 4.0% Experiment 3: Percentage Sucrose in Solution (%) Mass of potato before (g) Mass of potato after (g) Change in Mass (g) Change in mass (%) 0% 7.27 7.72 + 0.45 + 6.2% 5% 7.25 7.23 - 0.02 - 0.3% 10% 7.24 7.04 - 0.20 - 2.8% 15% 7.25 6.33 - 0.92 - 12.7% 20% 7.29 6.93 - 0.36 - 5.0% Averages: Percentage Sucrose in Solution (%) Mass of potato before (g) Mass of potato after (g) Change in Mass (g) Change in mass (%) 0% 7.33 7.71 + 0.38 + 5.18% 5% 7.44 7.53 + 0.09 + 1.21% 10% 7.21 7.11 - 0.10 - 1.39% 15% 7.32 6.86 - 0.46 - 6.28% 20% 7.45 7.00 - 0.45 - 6.04% I decided not to measure the temperature of each of the concentrations of water but I measured the temperature of the science lab hourly to see if an increase or decrease in temperature could explain any anomalies. Here are the hourly temperature measurements: Time Temperature (�C) 9:30 a.m. 23 10:30 a.m. 23 11:30 a.m. 25.5 12:30 p.m. 25.5 1:30 p.m. 29 Analysis and Conclusion I recorded the results that I obtained from doing the control experiments in a table, and I felt it was unnecessary to present them on a graph, as there were only two repeats. However, they did show me that there is not a very large increase or decrease in mass when the potato has been boiled, due to the cell membrane having been destroyed. The first potato cylinder lost 3.2% of its mass, which agreed with my prediction as I stated that the mass would decrease slightly, as some potato may break off, but no osmosis would take place. ...read more.

Conclusion

However, it was quite hard to try and keep all variables other than concentration the same, for example cutting the cylinders exactly the same size was rather difficult. It was hard to try and judge how much I should roll the cylinders on the paper towels before I weighed them, as I knew that they were so small that I bit of water could change the mass dramatically, and therefore compromise the reliability of my results. If I were to repeat the investigation I would not significantly change my method because I felt it was a good way of measuring osmosis. I would probably change the readings that I took, so that I had a lot more results to analyse and draw conclusions from. I would obviously need more time to take more readings, and the concentrations I would use are: * 0% sucrose * 2.5% sucrose * 5.0% sucrose * 7.5% sucrose * 10.0% sucrose * 12.5% sucrose * 15.0% sucrose * 17.5% sucrose * 20.0% sucrose * 22.5% sucrose * 25.0% sucrose I am unsure whether it is possible to have more than 20% sucrose, but I would like to try, as it would be interesting to see if the line produced on the graph would level out and become horizontal if the cells could not lose any more water. To support my conclusion by obtaining more evidence I could still investigate change in concentration of the solutions, but as well as measuring the percentage change in mass, I could measure the percentage change in length of the potato cylinders. I would use callipers to measure the change, and according to the theory behind osmosis, the cells would also expand and become turgid, causing an increase in size and length. I would plot a graph of my results, and like this investigation I could plot change in concentration against percentage change in length. This additional work would help make me more certain of my conclusion as it would show me that the cells expand in size as they take in water by osmosis. ...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)

*****
Great attention to detail is shown in this write up together with the use of appropriate biological terminology throughout. A few small numerical errors.

Marked by teacher Adam Roberts 10/05/2013

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)

    Therefore the smaller the error bars the smaller the error. Suitability of Method My method was quite suitable for the experiment it did allow me to gain a suitable and sufficient result.

  2. Marked by a teacher

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

    4 star(s)

    I expected the mass difference in the potato pieces in water to increase more then it did, but my results make sense. Cells have a concentration of 90% water and around it was 100% water, therefore not much diffusion was needed to balance to concentrations of the water in the cells and around the cells.

  1. Marked by a teacher

    To investigate how varying the concentration of sucrose solutions affects the rate of osmosis ...

    3 star(s)

    Observing plant cells in concentrated sugar solutions under a microscope, we can see that the contents of the cells have shrunk and pulled away from the cell wall causing the cells to become plasmolysed. This is so because water continues to leave the cell, the cell membrane gradually draws away

  2. Marked by a teacher

    Investigation to find the isotonic point of potato cells

    3 star(s)

    -0.34 -21.30 0.40 1.63 1.20 -0.42 -26.42 0.50 1.59 1.08 -0.49 -32.33 0.60 1.60 1.08 -0.55 -32.50 Concentrations As the salt concentrations weren't made up, we had to make them up ourselves. Here is a table to show the different concentrations.

  1. An investigation into osmosis using a pealed potato and different concentrations of salt solution.

    * Leave in the concentrations for roughly 24hours, but to have the exact time, record the time to the minute when the potatoes are placed in and taken out. * When potatoes are taken out of the solutions record the time and work out how long they have been in the solutions for.

  2. The Effect of Different Concentrations of Sucrose On Visking Tubing

    My prediction is therefore correct. From my graph, you can see the change in mass is affected by the solution. I can also say that the concentration of sucrose in the cells is just below 0.3 moles. I found this out from my line of best fit, as the point in which it crosses is the concentration of the Cells.

  1. Water potential of potato tuber cells - the weighing method.

    As the solution was very dilute it had .....more water molecules than that of the potato tuber and therefore b the .....laws of osmosis the water moved from an area of high concentration .....(Surrounding solution) to an area of low concentration (Potato .....tuber)causing the potato tubers mass to increase by an average of 11%.

  2. Find the concentration of Potato Cell Sap.

    my six points are on the line and the other two points are extremely close to the line, ( 0, 0.2, 0.3 and 0.5 are are on the line, whilst, 0.1 and 0.4 are next to the line). The line of my graph is straight and crosses the x axis,

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