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

Discovering the Lowest Concentration Of Lead Ions Needed to Cause the Loss of Partial Permeability of Red Onion Cell Membranes

Extracts from this document...

Introduction

Discovering the Lowest Concentration Of Lead Ions Needed to Cause the Loss of Partial Permeability of Red Onion Cell Membranes Aim: To discover the lowest concentration of lead ions needed to cause the loss of partial permeability of red onion cell membranes. Prediction: I predict the lowest concentration of lead ions to cause the loss of partial permeability in red onion cell membranes to be 0.4M Background Knowledge Lead ions reduce the partial permeability of cell membranes. The principle mechanism by which lead does this is by reduction in pore size and by reducing the solubility of the phospholipid bilayer, the principle material from which cell membranes made. Pores are proteins which allow uninhibited access to water molecules to and from the cell. These proteins contain thiol groups (-SH), to which lead ions have a particular affinity. A reduction in solubility reduces the permeability of the cell membrane to water; a less polar phosphate group on the head of the phospholipid repels the polar water molecules. ...read more.

Middle

This slightly moist red layer should be cut up into 6 small pieces (around 5mm2 should be sufficient) with the scalpel. 4. Immersion in Distilled Water (5 minutes), and Lead Nitrate (8 minutes) Immerse each membrane in water for 5 minutes to ensure each cell is turgid. Put a piece of membrane in the evaporating dishes of lead nitrate for 8 minutes (use the stopclock). The 0M lead nitrate solution will act as the control for the experiment. 5. Immersion in Glucose Solution (2 minutes) Convey the membrane into the glucose solution for 2 minutes (stopclock). 6. Check for % Plasmolysis by Microscopy Put a membrane under the microscope. Align the cells with the graticule, and count how many cells on the graticule line have plasmolysed, and how many have not. Convert to a percentage as below, and record in the table. No. Plasmolysed * 100 = Percent Plasmolysed Total No. Of cells Repeat for each of the other membranes, making sure not to mix them up. ...read more.

Conclusion

Table of Results (to be filled in) Lead Concentration (M) After 2 minutes submersion in glucose solution After 2 minutes submersion in distilled water 0 0.2 0.3 0.4 0.5 0.6 0.7 The percentage of plasmolysed cells in each case should be recorded in the table above. Graphs can easily be plotted (see sample below), to analyse data. Risk Assessment Lead Nitrate is toxic. Care should be taken so that it does not come into contact with skin. Avoid swallowing any. Scalpels are extremely sharp. Take care when cutting the onion. Reliability Reliable results are extremely important. Make sure that a new and uncontaminated glucose solution is used for after each bathing of the membranes, as lead could get into it and will build up as the experiment progresses. Although it is not critically important, make sure that each piece of membrane is around the same size. Any difference should be negated by the fact it is one cell thick, however. Ensure that all times are well kept to. Do not run over, especially in the glucose solution and distilled water, otherwise the percentage plasmolysed cells would be altered. ...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

    Beetroot Experiment. The purpose of this experiment is to determine the effect of temperature ...

    4 star(s)

    This effect could be a result of what is called freezing injury. At colder than normal temperatures the plasma membrane undergoes contraction. It is thought that intrinsic proteins which span the two sides of the plasma membrane may become damaged and break down.

  2. TEMPERATURE ON BEETROOT PERMEABILITY

    This anomalous result may have occurred due to the fact that we didn't get an accurately straight beetroot, because some of the beetroot when cut were "wobbly". This would have affected the shape of the beetroot resulting in different rates in which the beetroots membrane is damaged for each of us in the class.

  1. To investigate one of the factors that affects the permeability of cell membranes.

    This will be seen by an increase in the darkness of the red that the surrounding water will turn to, because as the permeability increases and more of the pigment leaks out, the surrounding water will begin to look darker.

  2. Investigating the permeability of plant cells.

    Facilitated Diffusion. Facilitated diffusion utilizes membrane protein channels to allow charged molecules to freely diffuse in and out of the cell. These channels come into use with small ions and in molecules. The speed is dependant on the limited number of protein channels available, whereas the speed of diffusion is dependant on the concentration gradient alone.

  1. Discovering the Lowest Concentration Of Lead Ions Needed to Cause the Loss of Partial ...

    Lead ions reduce the partial permeability of cell membranes. They do this by reducing the size of channel proteins and by reducing the solubility of the phospholipid bilayer. Channel proteins allow uninhibited access of water molecules to and from the cell.

  2. Investigation to determine the lowest concentration of lead ions that causes cell membranes to ...

    This pressure can build because of the rigidity of the cell wall. The cells within a plant that contain high water pressure act as the plant supportive structure, helping to give it its shape. With the loss of this osmotic pressure the supportive structure of the plant is lost and the plant becomes limp and shriveled.

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