Biochemical Tests for Molecules Flashcards
1
Q
Starch
Iodine test
A
- 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
Q
Protein
Biuret test
A
- 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
Q
Lipid
Emulsion test
A
- 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
Q
Glucose
Test strips
A
- 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
Q
why are glucose test strips useful?
A
- useful to test a person’s urine for glucose to indicate if person has diabetes
6
Q
reducing sugar
Benedicts test
A
- 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
Q
what is a more accurate method to compare the amount of reducing sugars in different solutions?
A
filter the solution and weigh the precipitate
8
Q
Non-reducing sugars
Benedicts test
A
- 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