Required Practical Activity 4 - Use qualitative reagents to test for a range of carbohydrates, lipids, and proteins Flashcards

Paper 1

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1
Q

What is the apparatus needed to use qualitative reagents to test for a range of carbohydrates, lipids, and proteins

A

-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

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2
Q

What is the method used to test for starch?

A

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.

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3
Q

What is the method used to test for glucose (simple sugars)?

A

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.

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4
Q

What is the method used to test for protein?

A

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.

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5
Q

What is the method used to test for lipids?

A

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.

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6
Q

What is the colour change for positive starch test?

A

Orange/brown - blue/black

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7
Q

What is the colour change for positive glucose (sugar) test?

A

Blue to brick red

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8
Q

What is the colour change for positive protein test?

A

Blue to lilac/purple

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9
Q

What is the colour change for a positive lipid test?

A

Colourless - cloudy white precipitate

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