Practicals

Question 1

What is the test for starch?

Answer 1

Iodine turns orange/brown to blue/black

Question 2

Test for reducing sugars and non-reducing sugars ?

Answer 2

For reducing sugars, eg fructose/glucose/maltose
Add Benedict’s solution, heat in water bath to 80 degrees for 5 minutes.
Turns blue, green, yellow, orange, brick red for positive
Semi-qualitative test

For non-reducing sugars eg sucrose, add HCl, then neutralise with an alkali, then do as above

Question 3

Test for proteins?

Answer 3

Biuret turns blue to purple

Question 4

Test for lipids?

Answer 4

Add ethanol and water. Goes cloudy white for positive

Ethanol dissolves lipids, dissolved lipids are water insoluble so come out of solution