Investigating The Effect Of Temperature Change On The Permeability Of Beetroot Cells.

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Luqman Patel

A/S  Biology

Investigating The Effect Of Temperature Change  On The Permeability Of Beetroot Cells.

 

Aim

This investigation aims to determine how an increase in the surrounding temperature affects plasma membrane of a typical plant cell structure.

Hypothesis

Increasing the temperature above a certain extent will damage and denature the plasma membrane and cause the cytoplasm and other substances contained within the membrane to leak out.

Introduction

Beetroot has a red pigment (anthocyanin) stored within its cells; it is prevented from leaking out by its cell membrane. The membrane is an extremely thin layer (8 to 10 nanometers (nm)) thick which is partially permeable. As we know, cell membranes are made up of lipids and proteins, and proteins tend to be affected by temperature. This investigation intends upon finding out if temperature has any effects on the permeability of beetroot cells, my prediction is that it does. This is because when the temperature is increased, a number of bonds in the protein molecules of the cell membrane are weakened. The first affected are the long range interactions that are necessary for the presence of tertiary structure. As these bonds are first weakened and are broken, the protein obtains a more flexible structure and the groups are exposed to solvent (water). If heating ceases at this stage the protein should be able to readily refold to the native structure. But if heating continues, some of the cooperative hydrogen bonds that stabilise helical structure will begin to break. As these bonds are broken, water can interact with and form new hydrogen bonds with the amide nitrogen and carbonyl oxygen groups of the peptide bonds. The presence of water further weakens nearby hydrogen bonds by causing an increase in the effective dielectric constant near them. As the helical structure is broken, hydrophobic groups are exposed to the solvent, and thus the pigment escapes readily. The following passage shall explain how the practical experiment is to be performed:

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Apparatus Required

  • 6 test tubes (Label A – F)
  • A Beaker
  • Thermometer
  • Bunsen Burner, Fireproof Mat, Gauze, stand
  • A Tile, Scalpel
  • Test tube rack
  • Pipette
  • Beetroot cores cut into discs of approx. 1mm thickness
  • Cuvettes (Colorimeter)  
  • Measuring tube

Plan

  1. Cut the Beetroot cores into discs (1mm thickness approx). Try making sure as far as possible that they are all of the same diameter and thickness, so as to reduce any errors unrelated to the actual aim of the experiment.
  2. The slicing of Beetroot into discs will ...

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** Plan only included. This plan includes a fairly detailed method but is lacking in a number of key elements that would be expected for A level coursework. To improve The inclusion of background research beyond that found in most A level textbooks is expected to help inform the plan. References should be included. The aim/ hypothesis needs to be clearly stated in terms of the dependent and independent variables. There should be a full consideration of the key experimental variables and how they are to be controlled. The apparatus that is to be used should be justified as well as listed. There is no attempt to assess safety and this is usually expected in newer mark schemes. The method mentions a pilot experiment. If this has been carried out the results should be included and discussed.