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Bio Molecules Tests
| Question | Answer |
|---|---|
| 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. |