• Join over 1.2 million students every month
  • Accelerate your learning by 29%
  • Unlimited access from just £6.99 per month

permeability of beetroot membranes

Extracts from this document...

Introduction

An investigation into how the concentration of a solution affects the rate of osmosis in a potato Definitions of important terms: Osmosis: Osmosis is the movement of water through a partially permeable membrane from a low concentration into a high concentration. This continues until both solutions are of equal concentration. Osmosis is a natural occurrence that can be simulated with an artificial membrane such as a visking tube. The rate of osmosis can be determined by the difference in water potential between the two substances on either side of the partially permeable membrane. Water potential (symbol??): Water molecules possess kinetic energy, which means that they are continually moving around when in a gas or liquid state. The higher the concentration of water molecules in a system, the greater the total kinetic energy of water molecules in that system and also the higher its water potential. Water potential is a measure of the energy available in an aqueous solution to cause the migration of water molecules across a semi-permeable cell membrane during osmosis. Water moves from areas of high (less negative) to areas of low (more negative) potential. Pure water is given the value zero. Aim of My Experiment: I am going to study whether or not the amount of water that may be taken into a potato cell by osmosis is affected by the concentration of a solution on one side of the partially permeable (cell) membrane. For this experiment I am going to use slices of potato as my partially permeable membranes and glucose solutions. MY PRELIMINARY EXPERIMENT For this investigation it was necessary to carry out a preliminary experiment in order to both gain a rough idea of what my result might be for the final experiment and to refine the method and techniques used in this experiment. This first experiment was carried out in class and the method used is a great deal less accurate than I hope to make my final experiment. ...read more.

Middle

Concentration of glucose solution (M) Weight of filter paper (g) Weight of paper + potato disks (g) Weight of potato disks (g) Original weight of potato disks (g) Change in weight (g) 1.00 M 0.58 g 2.89 g 2.31 g 3.07 g - 0.76 g 0.80 M 0.71 g 3.49 g 2.78 g 3.35 g - 0.57 g 0.60 M 0.66 g 3.45 g 2.79 g 3.04 g - 0.25 g 0.40 M 0.59 g 2.74 g 2.15 g 2.91 g - 0.04 g 0.20 M 0.63 g 3.83 g 3.20 g 3.18 g +0.02 g 0.00 M 0.70 g 4.46 g 3.76 g 3.28 g +0.48 g The percentage changes in mass were as follows: Concentration of glucose solution (M) Change in mass in percentage (%) 1.00 M - 24.76 % 0.80 M - 17.19 % 0.60 M - 8.34 % 0.40 M - 1.99 % 0.20 M + 6.29 % 0.00 M + 14.63 % Analysis The first observation I made was after the potato cylinders had been placed in their solutions for a few hours. The potato disks in the 0.00M, 0.20M and 0.04M glucose solutions were floating and the potatoes in the 0.60M, 0.80M and 1.00M solutions were at the bottom of the test tube, this lead me to drawing my next conclusion.From my experiment it is clear that as the concentration of the glucose solution increases, the mass lost by the potato increases. The loss in mass can only be reliably attributed to a loss of water from the cells of the potato because no other substances are able to pass through the potato's partially permeable membrane. The potato cells floated if they had lost mass, and were lower down in the test tube the more mass they had gained. In my explanation I have used the examples of potato cell walls for partially permeable membranes, and glucose solutions and the contents of the potato cells provided the two substances on either side in my experiment. ...read more.

Conclusion

It could well be the case that one or two of the potato disks in the test tube with 0.40 moles/dm3 glucose solution had a slightly greater surface area due to the angle at which they were cut. Apart from these causes, there may be others that are not factors which directly affect the rate of osmosis. Firstly, when I dried off the excess water on the potato cylinders after the experiment and before I weighed them, I used a paper towel. This might have either taken some water out of the potato or it might have left some excess water on the potato. This part of the experiment is difficult to come up with an accurate and fair method, as other ways would also lead to some slight mistakes. Another way of improving the results would have been to leave the experiment running longer, this would have enabled me to find the saturation point (when the potato can no longer take in any more water) and dehydration point (when the potato cannot lose any more water) and therefore get a more accurate result. In my preliminary experiment I used four potato disks in each test tube and varied the glucose concentrations by 0.25 moles each time. Although this preliminary experiment was useful to collate the data I later obtained in my final experiment, they were surplus results as the number of disks I used in my final experiment ensured that any anomalies hardly affected my results at all. Finally, I could extend the experiment to a more exact level by looking at the potato cylinders under a microscope, and then I would be able to see the cells in greater detail and draw some more observational results. From studying the possible causes for the anomaly in my experiment I have concluded that the most likely cause is human error in cutting the potato disks, or a change in temperature for the test tube in question. ?? ?? ?? ?? Georgia Barnett ...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

    Investigate the water potential of celeriac.

    5 star(s)

    This is because the temperature affects the amount of kinetic energy. For example if the temperature in test tube A is higher than the temperature in test tube B and assuming every other factor was constant, the water molecules in test tube A will have more kinetic energy and therefore osmosis will occur quicker.

  2. Marked by a teacher

    Human Reproductive System

    4 star(s)

    The sperm fuses with the oocyte, enabling fusion of their cell membranes and preparing for the fusion of their genetic material. Within 12 hours, the first meiotic cell division takes place, causing a rapid cell division which results in the formation of morulla cells.

  1. Marked by a teacher

    The Effect Of Temperature On The Permeability Of The Cell Membrane

    3 star(s)

    The fatty acid tails function as a barrier to water-soluble substances. The molecules move in and out of the cell by diffusion, osmosis and active transport .The kinetic energy of the molecules provide the energy for the movement. The membrane is composed of 40% lipids, 0-10% carbohydrates and 50-61% protein.

  2. Peer reviewed

    Effect of Caffeine on the Heart Rate of Daphnia

    3 star(s)

    As mentioned above, this may cause the Daphnia to develop a tolerance towards caffeine and thus affects the results in the experiment. To improve this, sufficient supply of Daphnia must be prepared to be used for the experiment. * Temperature of the environment of the Daphnia (water flea)

  1. Investigating Water Potential Of Potatoes.

    The unicellular protist Amoeba has both marine and fresh water species. The marine species are isotonic with seawater with the result that there is no loss or gain of water by the cell. The fresh water species on the other hand, are markedly hypertonic to there surrounding medium.

  2. Plan and carry out an experiment to investigate Osmosis in Potato tissue

    due to a time restriction the experiment can only be repeated twice. * Take the chips out of the sucrose solutions in the same order as they were put into the test tubes, because this means they will all stay in the solutions for the same amount of time.

  1. Osmosis in Potato cells

    Method of drying the potato. Final mass of the potato chip. Time in which each potato chip is left in the solution. Volume of the solution. Original length and original mass of each potato chip. Temperature of the room and solution for each potato chip.

  2. An investigation to demonstrate osmosis using a potato

    The weight of the purple coloured slice will be noted before and after immersion as described above. Similarly the blue and pink coloured slices will also be weighed in tube 1. This process will be repeated for tubes 2 to 6 and the results will be noted in a table and then plotted on a line graph.

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