• 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

Osmosis in Potato cells

Extracts from this document...

Introduction

ACCESS HUMAN BIOLOGY UNIT A Practical Assignment - Osmosis in potato cells Planning The aim of this experiment is to investigate the movement of water in and out of plant cells. The plant cells that we will use are potato cells. Osmosis is defined as the passage of water from a region of high concentration of water, to a region of low concentration of water through a semi permeable membrane. A semi permeable membrane is defined as a thin layer of material that allows some materials to pass through (such as water or some proteins) and prevents other materials from passing through (such as sugar or salt). The diagram below demonstrates osmosis taking place through a semi permeable membrane. Diagram taken from http://fig.cox.miami.edu/~lfarmer/BIL265/BIL2001/osmosis.JPG Plant cells are constructed with a thick cell wall and a central cavity filled with fluid, this can occupy over 80% of the volume of the cell. When osmosis takes place and water passes through the semi permeable membrane into the cell, the vacuole swells in size, pushing the cell contents against the thick cell walls and the cell becomes hard, this is known as becoming "turgid". The strong cell wall surrounding the cell prevents it from bursting. When the internal pressure is at its highest, the plant cell cannot accept any more water. This works against osmosis as it prevents further intake of water. This feature is important to plant cells as it is what causes plants to rise up towards the sunlight. When osmosis occurs and plant cells lose water, they become soft and are known as being "flaccid". The contents of the cell in this case shrink and pull away from the cell wall. In this state they are said to have "plasmolysed". When no osmosis occurs because the solution and the cell contain the same concentration of water, this is known as "Incipient plasmolysis". This occurs when plants are not watered (such as when you go away on holiday) ...read more.

Middle

Concentrations of solutions: * One solution was 100% pure distilled water and therefore 0% sucrose. * The second solution was 5% sucrose and 95% distilled water. * The third solution was 10% sucrose and 90% distilled water. * The fourth solution was 15% sucrose and 85% distilled water. * The fifth solution was 20% sucrose and 80% distilled water. We each took five potato chips to place one chip in each solution. When the experiment was completed, we shared our results with five others, thus obtaining a total of five results for each solution. Method: * We collected five test tubes and placed them in a test tube rack. * We labelled each test tube with the intended contents. * We made collected the solutions from each plastic container and measured 20ml of each solution using a measuring test tube and added to each test tube. * We collected a potato and it was cut into five equal chips for us using a scalpel, ruler and white tile. * We measured the length of each chip and made a note of the mass of each chip. * We placed the first chip in the first solution and noted the time of the start of the experiment. We waited one minute before placing the second chip in the second solution. We continued at one minute intervals until all chips were in the solutions. * After one hour had completed, we removed the first chip, dried it once pressing down firmly on a paper towel, measured its length with a ruler and took a note of its mass using a balance. One minute later we removed the second chip and did the same. We continued at one minute intervals until all chips had been removed and measured. * We then recorded our results in a table. * The equipment was then safely cleared away and we shared our results with five others until we had five sets of data. ...read more.

Conclusion

I feel that to improve the fairness of test, a potato chipper machine could be used or a crudit�s tool could be used to ensure the same thickness of chip were cut, they could then be cut to an equal length, lining them up to a square edge rather than being cut by hand measuring by eye as they were for our experiment. An additional point was the method used to time the experiment, we had to use a wall clock rather than a stop clock and so exact time measurements could not be made as it was difficult to see exactly when one minute had passed. To improve upon this point, I would use a stop clock next time. Although a varied range of sucrose solutions was used, I would like to use a wider range of solutions in order to determine exactly when plasmolysis occurred. I would also like to leave the chips in the solution for a longer time period in order to discover the saturation point of the potato cells. As the test tubes were open to the air, evaporation could have occurred and some solution could have been lost, to prevent this, bungs could be used to stop the test tubes. The temperature was not kept constant throughout the experiment, although I had planned to do so, this could be improved by possibly using a water bath to keep the temperatures the same throughout the duration of the experiment. A more consistent method of drying the chips could be used, rather than using paper towels and guessing that the same pressure was exerted on all chips to dry them. Different types of potato could be used to compare the results between them, or other varieties of vegetables or fruit. To conclude, the experiment was accurate and fair, however many changes and improvements could be made, as listed above. The experiment demonstrated osmosis had taken place, but with the improvements listed above, a more accurate set of results could be obtained. ...read more.

The above preview is unformatted text

This student written piece of work is one of many that can be found in our AS and A Level Exchange, Transport & Reproduction 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 AS and A Level Exchange, Transport & Reproduction essays

  1. Marked by a teacher

    Osmosis. Aim: To find the molarity of potato tubers cell sap. BIOLOGICAL ...

    4 star(s)

    I then placed 4 potato strips in each solution and covered it with a lid. I left the two sets for the later 10 minutes for osmosis to occur. After 10 minutes, I drained the Petri dishes and measured the new length and mass of the potato strips and noted them as final length and final mass respectively.

  2. Marked by a teacher

    The Effect Of Temperature On The Permeability Of The Cell Membrane

    3 star(s)

    gentle gradient, so this means that the diffusion rate of the pigment increases as the temperature increases, diffusion is the net movement of molecules from a region of high concentration (beetroot sample) to a region of low concentration (distilled water).

  1. Marked by a teacher

    What is Type 1 diabetes

    3 star(s)

    Do not hesitate to ask them for help and guidance. The most important aspect of treatment is the home blood glucose apparatus, which enables you to measure your own blood glucose levels and make any necessary adjustments to diet, level of exercise and insulin intake.

  2. Investigation on Osmosis using a potato.

    5 ml water 25 ml 1M sucrose solution. 1.34 1.19 -11.19 1 Molar sucrose solution. 0 ml water 30 ml 1M sucrose solution. 1.34 1.13 -15.67 A graph is shown below to compare individual results. These results show that there is a very good correlation throughout the different solutions and the line of best fit is very close

  1. Investigating osmosis on swede cells.

    Water potential is affected by both solute potential and pressure potential, and the following equation summarises the relationship between the two. ? = ?s + ?p Water potential = solute potential + pressure potential Osmosis in plant cells The main part of the body of many kinds of plants is a tissue called parenchyma.

  2. To find out the factors affecting the refractive index of liquid by using different ...

    already fixed, so that I do not have to measure it every time. The only variable is L1 and t. Here are my results: Temperature (t) (degree Celsius) Depth (d) (cm) Distance between points (L1) (cm) Distance between the normal line and the initial mark (L2) (cm) Horizontal distance (x)

  1. Fundamental human anatomy and physiology.

    Reference: http://training.seer.cancer.gov/module_anatomy/unit9_4_resp_passages.html Class notes hand out 26 / 2/ 2008 Web sight viewed on 27 / 2 /2008 * The respiratory system consist of the nose, mouth, throat, larynx, trachea, bronchi and lungs, therefore the function of the respiratory system is to help gaseous exchange to take place in the lungs and tissue cells of the body.

  2. Investigating Water Potential Of Potatoes.

    Scalpel,(used to cut the potato to the required length) 6. Borer,(used to cut the potato out, will give an even dimension to all the potato pieces cut out) 7. Balance,(used to weight the potato pieces before and after, recordings will be done to 2 decimal places.)

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