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

An Experiment to Determine the Water Potential of a Plant Tissue

Extracts from this document...

Introduction

Toby Nicholson An Experiment to Determine the Water Potential of a Plant Tissue Interpretation of results The graph shows that as the molarity of the sucrose solution increases the average percentage change in length decreases. In 0.0M solution the beetroot increases in length by an average of 5.3%, in 1.5M solution the average change in length is -10.9%; the beetroot has decreased in length. This trend can be explained by the idea of osmosis. Osmosis is the net movement of molecules from a region of higher water potential to a region of lower water potential, down a potential gradient, through a partially permeable membrane. When a beetroot strip in placed in a solution of low sucrose concentration (hypotonic), a solution with high water potential, the net movement of water molecules will be from the sucrose solution and into the cells of the beetroot through the partially permeable cell membranes via carrier proteins. Water molecules will move into the cells on the surface first increasing there water potential while the central cells still have lower water potential. The net movement of water molecules will continue into the deeper cells until equilibrium is reached through out all the cells when they all have equal water potentials. As a beetroot cell fills with water molecules, the protoplast swells so much it pushes against the cell wall, it becomes turgid (achieves full turgor) ...read more.

Middle

The molecules collide more often inside the cell so have more kinetic energy; therefore this increases the chance of water molecule hitting the cell membrane with enough energy to escape. This increases the water potential within the cell and reduces the net movement of water molecules into the cell. So we can say increasing pressure increases water potential. Conversely in hypertonic solutions, as water molecules leave the cell the pressure potential stays at zero. In conclusion, the average solution within the beetroot cells is 0.33 moldm-3. The general trend, that as molarity of sucrose solution increases average percentage change in length decreases, is described by osmosis. Also the reason the gradient decreases as molarity increases is due to increased pressure potential within a cell when it becomes turgid, which increases water potential. Evaluation The results obtained fell on or near to the curve of best fit on the graph except for the result obtained for 0.3moldm-3 sucrose solution, which was a higher value than the one before. This goes against the science outlined earlier. Therefore we can say this result is anomalous and has been circled on the graph. There are a number of reasons for this A large source of error within the experiment is the cutting of the beetroot strips. Due to the difficultly of cutting rectangular strips by hand with a scalpel not all the sides will be at 900. ...read more.

Conclusion

As well as measurements at more moralities, perhaps every 0.05 moldm-3, would have allow a more accurate curve to be plotted as there would have been more points. If the sucrose solution had not been shaken thoroughly enough the sucrose may not have dissolved completely and the molarity would have been different to what it was labelled. This would have cause inaccuracy. This is unlikely to have happen if the procedure was carried out well. A large potential source of error was due to that fact that the cells within beetroot have very varied water potentials because of the different amounts of salts and sugars in there vacuoles. This means not all of the strips would have had the same water potential so this varies the results and places another limit on the results. A different experiment would be to use the same procedure used above but use a pan balance and measure mass to 3 decimal places. This would create much less percentage error than measuring length. Another way off measuring the mean molarity concentration of cell sap within beetroot cells is to cut 'chips' of beetroot. Each one should be 5�5mm and less than 0.5mm thick. Place three chips into different molarity solutions and leave for about 30minutes. Then remove and using a microscope count to amount of plasmolysed cells per 200 cells. The molarity at which 50% of the cells are plasmolysed is the molarity within the cells. 1 ...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 Molecules & Cells 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 Molecules & Cells essays

  1. Marked by a teacher

    Aim: To estimate the solute potential of a plant tissue.

    However, in the overall view, the cells that were placed in the .3M solution came back with .01% of the cells plasmolysed and the cells that were placed in the 1.0M solution had 80% of the cells plasmolysed. Some of the major inaccuracies that have to be mentioned about this

  2. TEMPERATURE ON BEETROOT PERMEABILITY

    All of us in the classroom didn't put or remove our beetroot solution from the water baths at the same time. This is an error because some of us will have put the beetroot in the water bath for longer or shorter than required.

  1. An experiment to find of the isotonic point of root vegetables cells in contents ...

    at this concentration the water potential and solute potential are equal in the solution. At this concentration the net movement of water molecules into the root vegetable cylinder should equal those that will leave the root vegetable cylinder. The diagram above shows that equal amount of water molecules are entering and leaving the partially permeable membrane.

  2. To find out how different concentrations of sucrose solution affect the incipient plasmolysis of ...

    no net movement of water molecules if a partially permeable membrane is placed between the solution and the root vegetable. If the solution has a lower solute potential such as 0.3M sucrose solution, I predict that the root vegetables will become turgid and therefore increase the greatest in length and

  1. Investigating Osmosis.

    At the same temperature, smaller molecules will move more rapidly than larger molecules because it takes more energy to get the larger molecule moving. Other factors include any charges on the molecule (positive or negative) and the nature of the material that the molecules are moving through.

  2. Osmosis Coursework. Investigation to determine the water potential of apple tissue and carrot ...

    * Chairs/stools and any other unnecessary items (such as coats and bags) should be either tucked under the desks or placed out of the way, because the clutter could causes somebody to trip. * Any knives used in the experiment should be handled carefully and also stored safely when they aren't being used to avoid any cuts or stab wounds.

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