1.2.7 - Biochemical tests

Question 1

Test for reducing sugars

Answer 1

Add benedict’s solution containing copper 2+ ions
Heat in a water bath at 90
The reducing sugar reacts with the benedict’s and reduces copper 2+ to 1+
Colour change from blue to orange/red

Question 2

test for non reducing sugars

Answer 2

Heat with a few drops of HCl
neutralise with hydrogen carbonate
Produces sugars which are monosaccharides which will give a positive benedicts test

Question 3

Why do you heat with Hcl when testing for non reducing sugars?

Answer 3

Hydrolyses glycosidic bonds

Question 4

test for protein

Answer 4

Add biuret solution
will turn violet

Question 5

test for starch

Answer 5

Add iodine solution
will turn blue/black

Question 6

test for lipids

Answer 6

Add ethanol and shake
will turn a cloudy white colour