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Bio Molecules Tests

QuestionAnswer
What is the test for starch? Add potassium iodide to a sample, colour change will be from yellow-brown to blue-black. I2 forms a tri-iodide ion that slips into the middle of the amylose helix.
What is the test for reducing sugars? Heat with Benedicts solution (Copper II Sulphate), colour change will be from blue to brick red. Cu2+ reduced to Cu+ forming Copper Oxide.
What is the test for non-reducing sugars? Test for reducing sugar, if negative proceed to boil sample with HCl to hydrolyse into the monomer. Cool this and add Hydrogencarbonate. Test for reducing sugars again.
What is the test for lipids? Mix sample thoroughly with ethanol to put the lipid into solution. Filter and pour solution into water in a clean test tube. A cloudy white emulsion indicates presence of lipids.
What is the test for proteins? Place sample of food into a spotting tile well, add Sodium Hydroxide then Copper Sulfate. Colour change will be from blue to lilac. Colour is formed by complex between Nitrogen atoms and Cu2+ ions.
What is the quantitative test for reducing sugars? Use the centrifuge to seperate the precipitate and the supernatant, then use pipette to place supernatant into a curvette. Place curvette into the colorimeter and use a red filter to measure percentage transmission. Create calibration curve.
Created by: katieappleton