Qualitative Reagents - Systems in the Human Body

Question 1

How do you use the Benedict’s tests for sugars?

Answer 1

1) Prepare a food sample and transfer 5cm cubes to a test tube
2) Prepare a water bath so it’s set to 75 degrees
3) Add benedict solution to test tube using a pipette
4) Place test tube in the water bath using test tube holder, leave for five mins.
5) If food sample contains a reducing sugar, solution will change from blue to green, yellow or brick red depending on how much sugar is in the food.

Question 2

What colours does the blue benedict’s solution change to?
What is it testing for?

Answer 2

Green, yellow or brick red depending on how much sugar.
Sugar

Question 3

How do you do the iodine solution test for starch?

Answer 3

1) Make a food sample and transfer 5cm cubed to a test tube
2) add a few drops of iodine solution
gently shake the tube to mix contents
3) if the sample contains starch, the colour of the solution will change from browny orange to black or blue black.

Question 4

What colour does the iodine solution change to?
What is it a test for?

Answer 4

Blue black or black
Starch

Question 5

What’s the steps of Sudan III test for lipids?

Answer 5

1) Prepate food sample and transfer 5cm cubed to a test tube.
2) Add 3 drops of sudan III stain solution to test tube and gently shake
3) If sample contains lipids the mixture will separate into two layers, top would be bright red.

Question 6

What colour does the Sudan III top layer turn?
What is it a test for?

Answer 6

Bright red
Lipids

Question 7

How do you carry out the Biuret test for proteins?

Answer 7

1) Prepare a sample of food and transfer 2cm cubed to a test tube.
2) Add 2cm cubed of biuret solution to the sample and mix by gently shaking.
3) If food contains protein the solution will change from blue to purple.

Question 8

What colour does the biuret test turn?
What is it testing for?

Answer 8

Purple
Protein