Biochemical tests

Question 1

How to test for reducing sugars?

Answer 1

Add excess Benedict’s reagent(blue colour) and heat in water bath above 80C

Question 1

How to test for Nonreducing sugars?

Answer 1

Add Dilute HCL and heat in a water bath(to break the bonds and produce monosaccharides). Add NaOH(alkali) to neutralise. Add excess Benedict’s reagent and heat in water bath above 80C

Question 2

What is the positive result for testing sugars?

Answer 2

The colour would change from blue to green, yellow or red depending on the amount of sugar in the solution

Question 3

How to test for proteins?

Answer 3

Add excess Biuret’s reagent(blue colour, Dilute copper sulphate + sodium hydroxide) and shake and leave at room temperature

Question 4

What is the positive result for testing proteins?

Answer 4

The colour would change to purple if proteins are present

Question 5

How to test for lipids and what is the positive result for testing lipids?

Answer 5

Add ethanol, add water and shake for a minute

Question 6

How to test for starch?

Answer 6

Add Iodine

Question 7

What is the positive test for starch?

Answer 7

The solution turns blue-black