Required Practical Activity 4 - Use qualitative reagents to test for a range of carbohydrates, lipids, and proteins Flashcards
Paper 1
What is the apparatus needed to use qualitative reagents to test for a range of carbohydrates, lipids, and proteins
-Food: potato, carrot, crisps, biscuits, cheese
-Spotting tile
-Pipette
-10cm3 measuring cylinder or plastic syringe
-Beaker
-Boiling tubes
-Heating equipment
-Test tubes
-Iodine solution
-Benedict’s reagent
-Ethanol
-Biuret solution
What is the method used to test for starch?
1) Put a small piece of the food to test on a white tile.
2) Add two drops of iodine solution to the food.
3) If the iodine goes from orange-brown to blue-black, the food contains starch.
What is the method used to test for glucose (simple sugars)?
1) Mix a small sample of the food with 3 cm3 of Benedict’s solution in a boiling tube.
2) Heat the mixture in a hot water bath for 3 minutes.
3) If the solution goes from blue to brick red colour, the food contains sugar.
What is the method used to test for protein?
1) Mix a small sample of the food with 3 cm³ of biuret solution.
2) Leave for 2 minutes.
3) If the mixture goes from blue to a pale purple colour, the food contains protein.
What is the method used to test for lipids?
1) Mix a small sample of the food with 1 cm of ethanol in a dry test tube.
2) Pour the ethanol into a test tube full of cold water.
3) If the water goes from colourless to milky white, the food contains lipid.
What is the colour change for positive starch test?
Orange/brown - blue/black
What is the colour change for positive glucose (sugar) test?
Blue to brick red
What is the colour change for positive protein test?
Blue to lilac/purple
What is the colour change for a positive lipid test?
Colourless - cloudy white precipitate