Biology Unit 1 tests 3.0 / 5 based on 1 rating ? BiologyASAQA Created by: Fern RobertsCreated on: 11-05-13 17:49 Biuret Test Detects peptide bonds in proteins Mix a sample with Sodium hydroxide soloution at room temperature Add very dilute copper sulphate soloution Colour change from blue to purple shows presence of peptide bonds and therefore the presence of a protein 1 of 5 Reducing sugar test All monosacchairdes and some disaccharides are reducing sugars Get a sample of the sugar and HEAT GENTLY with Benedicts soloution Colour change from Blue to Red 2 of 5 Non-reducing sugar test Most disachharides are Non-reducing sugars. They will not produce a colour change in the reducing sugar test In order to detect a non-reducing sugar it needs to be broken down into monosaccarides by hydrolysis Add the sample to Hydrcholric acid and heat gently for 5 mins - will hydrolise the diasscahride into monosacchardies Add sodium hydrogencarbonate to neutralise the hydrocholric acid - Benedicts test will not work in acidic conditions Re-do the reducing sugar test : mix the soloution with benedicts reagnt and heat gently Once again if a reducing sugar is present it willl change the colour of the soloution from blue to red 3 of 5 Test for startch Add Iodine solotuion to the sample Colour change from yellow-blue/black 4 of 5 Emulsion Test Used to detect the presence of lipids Add 5cm of the sample to 5cm of ethanol and shake well - dissolves lipid in the sample Then add 5cm of water and gently stir A cloudy white precipitation indicates the presence of a lipid. If there was no lipid then there would be no precipitate. 5 of 5
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