Biochemical tests

Question 1

what can all sugars be classified as

Answer 1

reducing
OR
non-reducing

Question 2

what is the test for Sugars

Answer 2

Benedicts test

Question 3

what is the test for a reducing sugar

Answer 3

all monosaccharides are reducing sugars
1) add benedicts reagent( which is blue) to a sample and heat it in a water bath that has been brought to boil
2) if the test is positive it will form a coloured
precipitate

Question 4

what is an accurate way of comparing the amount of reducing sugars in differnt solutions

Answer 4

Filter the solution

and weigh the precipitate

Question 5

what is the colour from a positive non reducing sugar test

Answer 5

blue-> green-> yellow-> orange-> Brick red

Question 6

what is the test for a NON reducing sugar

Answer 6

1) get a NEW sample of the test solution and add HCL
2) heat it in a water bath that has been brought to boil
3) then neutralise it by adding sodium
4) then carry out benedicts test as you normally would
5) If the test is negative that means the solution will STAY BLUE ( doesnt contain any sugar)

Question 7

what is the test for starch

Answer 7

iodine test

1) add iodine dissolved in potassium iodide solution to the test sample
2) If starch is present the sample changes colour from browny-orange to blue- black

Question 8

what is the test for proteins

Answer 8

Biuret test

1) Firstly, the test solution needs to be alkaline so add a few drops of sodium hydroxide solution
2) Then add some copper sulfate solution

if protein is present TURNS PURPLE otherwise it will stay blue if not present

Question 9

what is the test for lipids

Answer 9

Emulsion test
1) pour the test substance and ethanol into a test tube then shake for a minute
2) then pour the solution into water
If lipid id present the solution will turn milky
OTHERWISE if not present then it will stay clear