- Test for proteins
- Positive result is when it turns from blue to lilac or purple.
- You add sodium hydroxide a
- to make sure it is alkaline
- you then add copper sulfate (detects the presence of peptide bonds)
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- Test for starch
- add iodine in potassium iodide solution
- If it is a positive result you will see a colour change from yellow-brown to blue black.
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- Test for lipids
- Mix the samples with ethanol in a test tube.
- Pour the sample into a clean test tube with water.
- If lipid is present a cloudy white emulsion will indicate the presence of lipids.
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- This is for reducing and non reducing sugars.
- You heat the reducing sugar with benedicts solution
- If a positive result occurs it will turn into a brick red precipitate (blue to green to yellow to orange-red)
- If you test for non reducing sugars;
- Test for reducing usgars first
- take a sample and boil it with HCL to hydrolyse the sucrose to glucose and fructose
- cool the solution and use sodium hydrogencarbonate to neutralise it.
- Test for reducing sugars again.
- Should form a brick red precipitate.
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