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To Identify Bio chemicals in an unknown substance

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To Identify Bio chemicals in an unknown substance Introduction The object of the experiment is to test a substance and identify the bio chemicals, which exist in that substance. Food tests are used to identify which bio chemicals exist in a substance. The substances characterised are in the tests are: carbohydrates, starch, lipids and peptide bonds. Method: The following tests were used to identify the relevant substances: Benedicts Test Carbohydrates - reducing sugars such as glucose fructose and maltose * Add 2cm3 of a solution to a test tube. * Add an equal volume of Benedicts solution. ...read more.


if above test is positive Starch Test Starch * Add 2cm3 1% solution to a test tube * Add a few drops of I2/KI solution. A blue-black colouration indicates starch present To Identify Bio chemicals in an unknown substance Method Lipids Test Lipids such as oils, fats and waxes. * Add 2cm3 of absolute ethanol to a test tube * Add 2cm3 of solution to the test tube * Dissolve the solution by shaking vigorously * Add an equal volume of cold water A cloudy white suspension indicates lipids are present Biuret Test Add 2cm3 of solution to a test tube Add an equal volume of 5% potassium hydroxide solution and mix Add 2 drops of 1% copper ...read more.


The Ph turned red indicating a Ph of 1. Sufficient sodium hydroxide was added until the litmus paper turned olive green indicating a neutralised solution. The Benedict's test was carried out on the neutralised solution. The solution turned orangey red after heating, indicating a positive result. Starch test After the I2/KI solution was added there was no change to the substance it did not have a blue-black colouration indicating a negative result. To Identify Bio chemicals in an unknown substance Results Lipid test After dissolving the solution in ethanol a cloudy white suspension did not form, indicating a negative result. Biuret test After adding potassium hydroxide and copper sulphate no colour developed indicating a negative result. Conclusion The unknown substance is a protein containing both reducing and non-reducing sugars. 1 ...read more.

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