Paper 1- Practicals Flashcards
How would you test for proteins in a sample?
Add Buiret reagent, originally blue
Shake mixture
If it turns from blue to purple, it contains protein
How would you test for lipids in a sample?
Add ethanol and water
Shake mixture
White emulsion formed if lipid is present
How would you prepare a sample of food to be tested?
Grind up sample with pestle and mortar
Mix with water
Filter with funnel and filter paper
How would you test for starch in a sample?
Add iodine solution, naturally brown
Turns from brown to blue-black
How would you test for sugars in a sample?
Add Benedicts Reagent , naturally blue
Bill test tube in hot water bath
If sugar is present, solution turns brick red
What does amylase break down?
Starch into simple sugars
What solutions do you put into the 3 different test tubes?
2cm of starch solution
2cm of amylase solution
2cm of pH 5 buffer solution
How long and at what temp do you place the 3 test tubes in the water bath for?
30ºC for 10 mins
How long do you leave the combined mixtures in the water bath for?
30 seconds
How long are the intervals between each drop of solution onto iodine?
30 seconds
What do you change when you repeat the experiment?
The pH buffers (use 6,7,8)
What are 2 problems with the amylase experiment?
- 30 seconds- only approximate time for when the reaction completed
- Colour change gradual- difficult to see when reaction has finished
Why must the samples be left in the water bath before solutions are mixed?
To allow temperature to equilibriate
What is a buffer solution?
A solution which can resist changes in pH
What do you place the cut pondweed into?
Boiling tube containing sodium hydrogen carbonate solution
