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Why did the colour leak out of cooked beetroot?

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Aim: The objective of this investigation is to find out, "why does the colour leak out of the cooked beetroot?" and the aim of this is to investigate the effect of temperature on cell membrane. This experiment allows us to see the permeability of the membrane structure of beetroot. Beetroot contains red pigments called betalains, located within the cell vacuole. Normally, the pigment cannot pass through membranes but they leak out when the beetroot is boiled. And therefore by observing the beetroot under different temperature, I will be able to determine the effect of temperature on cell membranes. Hypothesis: As the temperature increases, so does the percentage absorbance of the beetroot pigments. Fair testing: Definition: 'Fairness' implies that the outcome of the activity truly depends on what is being investigated, and is not being distorted by other external factors. Therefore a fair test is one where all the variables are kept constant or the same, except the variable that is being investigated. A variable is anything that can change and which may influence the outcome of the investigation. List of variables: The different variables are: > The amount of distilled water > The temperature of the water > The length of the beetroot. - 1 cm in length Variables that needs to be controlled (independent variable) ...read more.


2 Place the slices in a beaker of distilled water. Leave overnight to wash away excess dye. 3 Next day, place eight labelled boiling tubes each containing 5 cm3 distilled water into water baths at 0 ?C, 10 ?C, 20 ?C, 30 ?C, 40 ?C, 50 ?C, 60 ?C and 70 ?C. Leave for 5 minutes until the water reaches the required temperature. Place one of the beetroot sections into each of the boiling tubes. Leave for 30 minutes in the water baths. 4 Remove beetroot sections; shake the water/solution to disperse the dye. 5 Switch on the colorimeter and set it to read % absorbance. 6 Set the filter dial to the blue/green filter. 7 Using a pipette accurately, measure 2 cm3 distilled water into a cuvette. Place the cuvette into the colorimeter, making sure that the light is shining through the smooth sides. 8 Adjust the colorimeter to read 0 absorbance for clear water. Do not alter the setting again during the experiment. 9 Place 2 cm3 of the dye solution into a colorimeter cuvette and take a reading for absorbency. Repeat the readings for all the temperatures. 10 Present your results in an appropriate way. Prediction: I predict that as we increase the temperature of the water solution more pigment will leak out. ...read more.


To control all this man made errors, the best way to obtain precise readings is by taking the reading from the calorimeter more than once after taking out the beetroot from the test tube. So basically, I repeated my experiment twice for accuracy and there were no anomalies. But still there are many things that could have affected my results and these are as follows: * The length of beetroot cut out - if a larger length was cut, more of the pigment would have been released increasing the percentage absorbance. * The temperature of the water was not constant as it wasn't left for the specified 30 minutes. To further improve my results or to have more confidence in my conclusion I could have done the following: 1. I could have taken measurements in shorter temperature intervals for example instead of measuring from 10?C, 20?C, 30?C ---- I could have used 0?C, 5?C, 10?C and so on... with an interval of 5?C. 2. I also could have done the same experiment perhaps with another plant to see if the relationship between the temperature and its effect on cell membranes are the same. 3. The experiment can be modified - using different apparatus such as a more accurate colorimeter, which measures light at narrow range of frequencies. ...read more.

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