Experiments Flashcards
What does Benedicts test detect?
Reducing sugars. These include all monosaccharides and maltose.
What is observed when Benedicts reagent is positive?
The blue reagent will go through the sequence blue-green-yellow-orange and finally will form a brick red precipitate.
How do your complete Benedicts test?
Add an equal volume of Benedicts reagent to the test solution and heat to at least 80°C in a water bath.
What is the test for non reducing sugars?
Use Benedicts reagent.
Test for the presence of reducing sugars initially.
If none present, hydrolyse the rest of the sample by heating with dilute hydrochloric acid in a water bath.
Once cooled, neutralise by adding sodium hydrogencarbonate.
Test with Benedicts solution.
If a non reducing sugar is present there will be no colour change (blue to blue).
What is the test for starch?
Iodine.
How do you test for starch?
Add iodine solution.
If starch is present colour will change from yellow-brown to blue-black.
What is the test for protein?
The biuret test.
What does the biuret test detect the presence of?
Peptide bonds.
How do you do the biuret test?
Add potassium hydroxide to the test sample.
Add a few drops of copper sulphate solution.
Observe.
What is the colour change in the biuret test?
Blue to mauve/lilac.
How do you prepare a chromatogram?
The chromatography paper is cut to fill the tank.
Ensure that the chromatogram is long enough to just touch the solvent at the bottom of the tank.
A horizontal line should be drawn in PENCIL above the base of the chromatogram, above the solvent.
The solution containing amino acids needs to be spotted on the pencil line. This allows the solution to be concentrated.
