biochemical tests Flashcards
1
Q
Test for Starch
A
- Add Iodine solution
- Colour change
orange 》 blue-black
2
Q
Test for Protein
A
- Add Biuret A
- Add Biuret B
- Colour change
blue 》 lilac
3
Q
Emulsion Test for Lipids
A
- Add ethanol
- Shake
- Add water
- Shake
- Colour change
clear 》 milky/cloudy white emulsion
4
Q
Test for Reducing Sugars
A
- Add Benedict’s reagent
- Heat for 2 mins in a water bath at boiling point
- Colour change
blue 》 BRICK RED, orange, yellow, green
5
Q
What are Reducing Sugars?
A
- ALL monosaccharides
- SOME disaccharides (maltose/lactose)
- NO polysaccharides
6
Q
Test for Non-Reducing Sugars
A
- Add a few drops of dilute HCl
- Heat in a water bath at boiling point for 2 mins
- Neutralise with sodium bicarbonate
- Add Benedict’s
- Heat again
- Colour change
blue 》BRICK RED, orange, yellow, green
7
Q
What are Non-Reducing Sugars?
A
- NO monosaccharides
- SOME disaccharides (sucrose)
- ALL polysaccharides
8
Q
How can you determine glucose concentration?
A
By producing a dilution series of glucose solutions of known concentrations
9
Q
Determine glucose concentration with dilution series [9]
A
- Perform Benedict’s test on each sample of a known concentration
- Using same volume of solution for each test
- Remove precipitate formed by filtering
- Use a colorimeter to measure the absorbance of each sample
- Calibrate colorimeter using unreacted Benedict’s
- The lower the absorbancy of the solution = more sugar present (as removed ppt)
- Plot absorbance against glucose concentration
- Plot a calibration curve
- Repeat with unknown sample, using graph to determine glucose concentration
