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Why does the colour leak out of cooked beetroot?

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Introduction

Why does the colour leak out of cooked beetroot? Purpose: To investigate the effect of temperature on the cell membrane structure Background: Beetroot contains red pigments called betalains, named after the Red beet (Beta vulgaris) located within the cell vacuole. Normally the pigments molecules can not pass through membranes as they are too big, but they leak out when beetroot is cooked. When you heat a beetroot, you disrupt the cell membranes. A biological membrane is made of a phospholipid bilayer containing protein, cholesterol, glycoprotein and glycolipids. 30% of the membrane is made of phospholipids and 70% is made up of proteins. The more unsaturated phospholipids there are in the membrane, the more fluid it becomes, as the 'kink' in the hydrocarbon tails of the unsaturated phospholipids prevent them from packing close together so more movement is possible. When you heat something you give it energy. Molecules start to spin and vibrate faster. The water will expand too. This will have a disruptive effect on any membrane in its way. Lipids become more fluid as temperature goes up, so the membranes become more fragile. Proteins are remarkable machines: they're formed of coiled and folded strings of amino-acids, held together by hydrogen bonds and di-sulphide bridges. ...read more.

Middle

7. Using a pipette, measure accurately 2 cm3 of distilled water into a cuvette. Place it into the colorimeter, without touching the bottom of the cuvettes so the bit light shines through is not smudged, making sure that the light is shining through the smooth side. 8. Adjust the colorimeter to read 100% transmission for clear water as the control, keep the setting through out the experiment. 9. Place 2 cm3 of dye solutions from each of the boiling tubes into cuvettes and take readings for transmission. Safety: * Use cork borer and scalpel carefully to prevent injuries by cutting * Water in some of the water baths would be very hot so watch out * Watch out that you don't break any glass apparatus to prevent cutting Results: Temperature �C % transmission 0 96 10 92 20 90 30 88 40 74 50 37 60 10 70 1 To plot the graph, I put independent variable (temperature �C) on x-axis and dependent variable (% transmission) on the y-axis Analysis: From my results and graph, I can see that my prediction was correct, the transmission of the solutions decreases and the absorbance increases as the temperature increases. ...read more.

Conclusion

If any errors were to occur from the equipment, i.e. systematic errors, the most likely would have been the temperatures of the water baths. The temperatures of these baths would not always have been constant and may have been slightly over or under the desired temperatures. This is because the heater on the water baths only start working once the temperature has dropped below what is required, once the heater has started working once again it causes the temperature to rise above what is required, then the bath once again cools to below the optimum temperature and the whole cycle starts once again. Also, for the 0�C, I used a beaker of ice cubes, but that didn't reach right down to 0�C, and some of the ice must have melted during the 30 min waiting time, raising the temperature. Also I have found that the colourmeter was particularly unreliable because during the testing numbers on screen changed often for each of the cuvettes, and it would be better to have a more accurate colourmeter too which measures light over a narrower range of wavelengths. To achieve a fairer and more reliable result, the experiment should have been repeated two times, working out a clear average between the results, seeing any trends more clearly. ...read more.

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