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Flashcards in Biochemical Tests for Molecules Deck (8)
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1

Starch
Iodine test

- add iodine dissolved in potassium iodide solution to test sample
- if starch is present, brown/orange to dark blue/black
no starch, stays brown/orange

2

Protein
Biuret test

- test solution needs to be alkaline so add few drops of sodium hydroxide solution
- add some copper (ii) sulphate solution
- if protein present (positive result), turns pale purple
- no protein (negative result), stays pale blue

3

Lipid
Emulsion test

- shake test sample with ethanol for about 1 minute then pour solution into water
- if lipid is present, solution turns milky
- more lipid, more noticeable the milky colour is
- no lipid, solution stays clear

4

Glucose
Test strips

- glucose tested using test strips coated in a reagent
- strips dipped in test solution and change colour if glucose is present
- colour change compared to chart to give indication of the concentration of glucose present

5

why are glucose test strips useful?

- useful to test a person's urine for glucose to indicate if person has diabetes

6

reducing sugar
Benedicts test

- reducing sugars include all monosaccharides and some disaccharides
- add Benedicts reagent (blue) to sample and heat it in water bath that's been brought to boil
- colour of precipitate changes from:
blue - green - yellow - orange - brick red
- if positive result, forms coloured precipitate
- higher the concentration of reducing sugar, further the colour change goes (used to compare amount of reducing sugars in different solutions)

7

what is a more accurate method to compare the amount of reducing sugars in different solutions?

filter the solution and weigh the precipitate

8

Non-reducing sugars
Benedicts test

- if negative result for reducing sugar then non-reducing sugar may be present
- firstly, have to break non-reducing sugars to monosaccharides
- add dilute HCL to new test sample and heat in water bath that's been brought to boil
- neutralise with sodium hydrogencarbonate and carry out benedicts test
- positive result, forms coloured precipitate
- negative result, stays blue so no sugar present