The Effect of Temperature on Beetroot Cell Membranes

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The effect of temperature on the cell membranes of beetroot cells and amount of pigment released.

Apparatus

• Corer size 4

• White tile

• A Beetroot

• Automatic Water Bath

• Segregated knife

• A thermometer

• Stopwatch

Method:

• First take the white tile and the corer. Then collect a cylinder of beetroot by pushing the corer into the beetroot and withdrawing it. The cylinder remains inside the corer- so push it out with the end of a pencil.

• Collect 3 cylinders, and then cut them into 6 pieces of 3 cm with a segregated knife.

• The beetroot was cut to 1cm. Because the beetroot has been cut some of the cell membranes had been broken, which means some anthocyanin will leak out. This must be completely washed off in order to maintain the reliability of the results.

• The water bath must then be heated to 20oC (the first temperature for the experiment)

• Once the water bath is at the correct temperature (measured using the thermometer), one piece of beetroot is placed into the hot water directly and left for exactly1 minute (using a stopwatch).

• The beetroot piece is then placed into a tube of 5 cm of distilled water.

This procedure will be repeated with the other four pieces of beetroot and the temperature should be changed accordingly. The temperatures will be using are 20oC, 40oC , 60oC and 80oC

Each time a piece of beetroot is removed from the heated water, it will be left in the distilled water for exactly 30 minutes, before being discarded.

The fluid in each of the test tubes will be analysed using a colorimeter and compared against the control, which is distilled water to check for any variations in the colour of the water.

The variables kept constant

• The same diameter corer is used so to keep the surface area of each beetroot piece the same size.

* When the beetroot has been cut some of the cell membranes are broken, which means some anthocyanin will leak out. This must be completely washed off in order to maintain the reliability of the results.

* I will use distilled water to so that I have a reliable substance to test with a colourimeter.

Results Table

To be added as I can't do one on my computer ( not good enough software)- I will use a computer at school.

Analysis

The reason why the amount of betalain pigment released (colourimeter reading) from the vacuole increased directly proportionally to the temperature of the water bath (from 20oC to 40oC) is because the amount of random movement of betalain molecules out through the cell membrane depends on the amount of heat energy the betalain molecules are given to convert into kinetic energy- hence the higher the temperature the more betalain lost from the vacuole.

This is because the betacyanin pigment of beet root cells is normally sequestered in the vacuole and by means of the cell membrane which maintains the integrity of the cell and the tonoplasts, it does not leak into the cytosol or the extra-cellular sap of the beet root. However when we increase the temperature the relatively weak forces holding the different parts of the polypeptide chains together (like hydrogen bonds, sulphur bridges and ionic bonds) can be disrupted very easily- this damages the vacuole and makes holes in the cell membrane, inducing leakage.

The cell membrane is also damaged and so diffusion of betalain occurs through the partially permeable membrane by osmosis- the betalain molecules move by diffusion from an area where they are more highly concentrated to an area where they are at a lower concentration, along a concentration gradient.

The reason why the amount of betalain pigment increases rapidly (from 40oC to 60oC) is because most mammalian protein's denature and tertiary structure unravels (the strong covalent bonds between the R groups of amino acids in the polypeptide chains are destroyed) at temperatures over 40oC.

The reason why the curve starts to flattens out (between 60oC and...
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