Tests Biological Molecules Flashcards
Preparing test for starch proteins and lipids
Small amount of distilled water with food and grind w mortar and pestle
Add more distilled water and filter out big food parts
Starch test
Add food solution to test tube
Add iodine and potassium iodide
If starch, blue-black
If not, remain orange
Protein test
Add solution to test tube
Add sodium hydroxide and copper sulfate
If protein - purple
If not protein - blue
Lipids
(Don’t filter food out)
Put food solution in test tube
Add ethanol and water
Shake
White cloudy emulsion - lipid
Remain clear - no lipid
Test for reducing sugars
Benedict’s test
Place food solution in boiling tube and add Benedict’s solution - cu2+
Place into beaker of boiling water for 5 minutes
If blue - no reducing sugar
If reducing sugar - red
Benedict’s test colours
Reducing sugar - blue bc add another copper ion
Green - small amount
If really high - brick red
Non reducing test
- Benedict’s test
- Add solution to another boiling tube
- add hydrochloric acid and boil in water for 5 minutes
- If non reducing - acid hydrolyses glycosidic bond and releases monosaccharides
- Add sodium hydroxide and ph paper to check if alkaline
- Add Benedict’s solution and heat for 5
Result non reducing sugar
IF… First test - blue and second test - orange —> non reducing present
First test - brick red, second test will be clear
Why do we add hydrochloric acid to solution for non reducing sugar
Bc if it is a non reducing sugar, the acid hydrolyses the glycosidic bond and releases monosaccharides
Why do we add sodium hydroxide in test for non reducing sugars
To see if it’s alkaline by using ph paper because Benedict’s test won’t work under acidic conditions
At what stages do we boil solution in test for non reducing sugar
When we add hydrochloric acid
When we add Benedict’s test at the end
What is a reducing sugar
Reducing sugar can donate an electron to another molecule
This is all monosaccharides and some disaccharides
