• 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)

    Repeat the above method at least another two times. Independent variable - we will control the molarity of the sucrose solution. We will use 5 different solutions of sucrose, 0.00, 0.25, 0.50, 0.75, and 1.00 mol dm-3. We will dilute the 1.00 mol dm-3 sucrose solution using water.

  2. Marked by a teacher

    The Effect Of Temperature On The Permeability Of The Cell Membrane

    3 star(s)

    Leaving the beetroot in distilled water for a suitable period of time will test this. The preliminary experiment will also help me decide how much water to use as too much water can dilute the colour of the beetroot too much, using too little water could make the water darker.

  1. Peer reviewed

    Effect of Caffeine on the Heart Rate of Daphnia

    3 star(s)

    The Daphnia should be handled with extra care as it is a very delicate creature. Muslin cloth is used in holding the Daphnia in position. This makes the Daphnia unable to move when observing it under the microscope, thus make the counting of heart beat or the beating of the legs easier.

  2. Investigating Water Potential Of Potatoes.

    Wilting is not to be confused with plasmolysis. Both involve the cells losing water, but for different reasons. In plasmolysis only the protoplast shrinks, leaving the cell wall behind. In wilting the whole cell, including the wall, shrinks and no gap develops between the plasma membrane and the cell wall.

  1. Osmosis in Potato cells

    Method of drying the potato. If some potatoes were dried a lot and some were not then the mass would differ as it would include the excess water, again making the results inaccurate. A method of drying the potato chips was agreed and all chips were dried in exactly the same way.

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

    Direct the laser pointer pointing towards the table. Put the container on a rack, with an A4 paper underneath the container. Draw a straight line of symmetry on the paper. Then adjust the light beam to make it shone on the line. Shone the beam and make a mark on the other side of the paper since I cannot move the container.

  1. 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.

  2. Investigation on Osmosis using a potato.

    In the case of this experiment if the water concentration is higher outside of the potato then the water will transport from the potato to the solution. In this case it will lose mass and it will start to do the opposite of osmosis which is plasmolysis.

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