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Biology Lab Design Glucose concentration

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Biology Lab Design Glucose concentration Name: Elric Balrog Introduction Carbohydrates can be divided into two major groups; sugars and non sugars. These two groups can further be broken down into monosaccharides and disaccharides. Reducing sugars are all monosaccharides. Monosaccharides contain carbon, hydrogen, and oxygen. The general formula is (CH2O2). Reducing sugars possess a free aldehyde group and include the sugars glucose, galacose, fructose and lactose. Benedict's reagent will be used to test the filtered juice extracts of different fruits for the presence of reducing sugar. In order to facilitate the experiment and to avoid doing serial dilutions, a colorimeter will be used to compare the colours obtained. It must be taken into account that ripe fruits will usually have a higher amount of reducing sugar. Apples have a free glucose content of approximately 2.4 g/100g, pineapples have a free glucose content of 1.7g/100g; which is lower than in apples. Teacher's Aim To find the concentration of reducing sugar in fruits General Aim To compare the amount of glucose concentration (reducing sugar) present in five different fruits. Hypothesis I predict that the amount of reducing sugar will be different in all 5 fruits as they all come from different varieties. ...read more.


the mixture was heated carefully using an electric water bath at 45�C for 5 minutes 7. A standard was obtained from the colorimeter using water 8. The contents of test tube S1 was poured into a cuvette and placed in the colorimeter 9. The reading was taken [depending on whether the colorimeter has an analog or digital meter, the output may be shown as transmittance (a linear scale from 0-100%) or as absorbance (a logarithmic scale from zero to infinity)] 10. The procedure was repeated with the remaining four fruits. 11. Results obtained were tabulated and a graph was drawn to compare the amount of glucose found in different fruits Order in which fruits were crushed: Apple, pineapple, passion fruit, orange, tomato The blender was washed before being used on other fruits. Protocol diagram CUVETTE JUICE & BENEDICT'S SOLN DISPLAY SCREEN SAMPLE COLORIMETER Protocol diagram showing colorimeter and cuvettes Photograph of experiment Table showing raw data (data collected was in absolute value) Fruit Reading 1 (ABS) Reading 2 (ABS) Reading3 (ABS) Reading4 (ABS) Reading 5 (ABS) Reading 6 (ABS) Reading 7 (ABS) Apple 2.00 2.00 2.00 2.00 2.00 2.00 2.00 Pineapple 1.26 1.64 2.00 2.00 2.00 2.00 2.00 Passion Fruit 0.18 0.20 0.38 0.20 2.00 0.23 0.20 Orange 2.00 2.00 2.00 2.00 2.00 2.00 2.00 Tomato 1.48 1.77 2.00 2.00 2.00 2.00 2.00 Processed data (showing percentage) ...read more.


In this case, passion fruit seed was seen to have 1.64% of glucose, fructose and sucrose sugars combined. This may have biased the final results. Replicate observations and multiple samples of fruit should have been tested. This would have given us a broader understanding of how glucose concentration in fruits could vary depending on their nature. When testing for reducing sugar, the fruit samples containing benedict's solution should have been placed in a boiling water bath at a temperature of 80�C for 5 minutes whereas in the experiment the water bath was only set to a temperature of 45�C. This may have caused a problem as the colour change from blue to a red precipitate could not have fully taken place at a temperature of 45�C. Two benedict's tests for each fruit juice should be done in order to obtain a more accurate average, as anomalies and discrepancies could be present in the results. We need to take into account the fact that different fruits come from different species; and discrepancies in the glucose concentrations may be present due to genetic variations. The species of one fruit containing the highest and the lowest amount of glucose should have been tested, and an average obtained. Overall, I believe that the experiment was very interesting yet more results from a wider range of fruits from different species of plant could have been used. ...read more.

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