Practicals

Question 1

Describe the Benedict’s test for reducing sugars

Answer 1

Add Benedict’s reagent to the sample.
Heat in hot water bath.
Colour change from blue to brick red precipitate.

Question 2

Describe test for non reducing sugar

Answer 2

Negative result: Benedict’s Reagent stays blue.
If sample is not liquid it must first be ground up in water.
Hydrolyse non reducing sugars into their monomers by adding HCL then heat in water bath.
Neutralise mixture by using sodium carbonate solution.
Then do Benedict’s test.
Positive result: will turn to red precipitate

Question 3

Describe how to test for lipids in a sample

Answer 3

Add ethanol to sample
Add water
Shake and observe colour changes
Positive result: cloudy white emulsion

Question 4

Describe biochemical test for proteins

Answer 4

Add biuret reagent to sample
Positive result is lilac colour