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Beetroot Core Practical (AS)

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Laura Pearson Write up of Activity 2.7 experiment 4th October 2006 Why does colour leak out of cooked beetroot? Introduction To answer this question I am going to be looking at the membrane structure of beetroot. All cells are surrounded by a cell membrane this structure separates the contents of the cell from the outside, the membrane has tiny holes in it which allows small molecules to pass through but not larger ones this is called a partially permeable membrane. Beetroot contains red pigments called betalains in the cell vacuole and normally do not pass through the membrane. However when cooked the dye leaks out and so I am investigating the effect of different temperatures on the amount of dye and the extent of damage on the beetroot membrane structure which causes the holes to allow larger molecules through. This diagram helps to describe the processes in the cell. At the moment the cell membrane is normal and the hydrophilic regions are pack tightly together with only small gaps large enough for water molecules to diffuse through. However once heated the bonds between these regions weaken therefore the gaps or permeability increases. As the concentration gradient is in favour of the test tube filled with distilled water the dye leaks out. ...read more.


Safety precautions During this experiment I have use a cork borer, a knife and water baths measuring 50 and 70 Centigrade in temperature. To ensure I cause no harm to others or myself, I cut the beetroot on a tile on the desk, whilst standing up. I also made sure no bags or books were on the floor in case I tripped with the glass beakers. When putting the test tubes in the water baths I held the top carefully and securely to ensure I didn't touch the water. Results After leaving the test tubes at different temperature for 30 minutes I took them out if their locations and took a sample of 2cm� and placed it in the colorimeter. I repeated my experiment 3 times as this will ensure I can work out an average for the 3 results and plot the average reading on a graph, this way my will be more valid. To ensure I collected the most accurate results possible I used the correct measuring instruments for each measurement, although they all have a certain degree of inaccuracy the equipment for instance my pipette, was 5cm� and I used this for the measuring of 2cm� and 5cm� as this is more accurate than using a 10cm� pipette. ...read more.


This is because freezing the beetroot first bursts the cell membranes as the water inside expands and then kills the cells, allowing the pigment to be extracted much more quickly. Errors that may have occurred in my practical are the measuuring of the different components. Place of error Percentage Error % Water baths 0.5/50*100 1 0.5/70*100 0.7 Pipette 0.5/2*100 25 0.5/5*100 10 Ruler 0.5/1*100 50 Colorimeter 0.05/0.88*100 5.7 0.05/0.07*100 71.4 0.05/0.02*100 250 0.05/0.05*100 100 0.05/0.92*100 5.4 Stop watch 0.00005/30*100 0.0002 From the table you can see that the majority of the equipment was to a high standard of accuracy and so my results can be relied apon to be fairly certain representative of events. The main limiting factors of my results was not enough different temperatured water baths if more had been tested I could have been more able to come to a valid conclusion as the trend would be more sound. Summary In this experiment I tested the effect different temperature had on the permeability of a beetroot membrane structure. I found out that as the temperature increases the more dye leaks out due to the bonds vibrating in the structure. This breaks apart the phospholipid bilayer creating larger holes in the membrane substainsial enough to allow the red pigments called betalains in the cell vacuole that do not normally pass through the membrane. ...read more.

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