Chapter 2 - Experiments Flashcards
How to test for fats?
Emulsion test
What is the emulsion test?
Add ethanol to potential source of fat, mix well to dissolve source of fat, pour mixture into another tube with water to make the emulsion
How to test for starch?
Iodine test
What is the Iodine test?
Mix a potential source of starch with some iodine (straw yellow colour) and if starch is present should turn blue/black, water for example would stay yellow
What is a colorimeter used for?
A colorimeter is a device used in colorimetry. It refers to the device that measures the absorbance of particular wavelengths of light by different biochemicals
How to use a colorimetry for glucose?
Use a range of different glucose concentrations (0.1/0.5/2.0), and to each tube add an equal amount of Benedict’s solution and heat all tubes to 80+ degrees for 9 mins
What do you do after different concentrations of solutions have been heated?
Wait to cool and pour contents of each tube into separate colorimeter tubes and in turn place in the colorimeter (which will give absorbance readings), do the same after with unknown to estimate the concentrations
How to use Benedict’s test for non-reducing sugars?
You must take observations at the start, immediately after adding Benedict’s solution and mixing, and after heating. Add 1M of hydrochloric acid to the sucrose and mix by heating and swirling; then add Benedict’s, and then re-heat
What is a non-reducing sugar?
A sugar e.g. sucrose, which is stuck with a cyclical structure, it cannot alter its structure in any way
What colour should pre-treated & heated sucrose turn to show its a non-reducing sugar?
A brick red cloudy precipitate
How to use Benedict’s test for reducing sugars?
Place equal volumes of the potential reducing sugar (glucose) and Benedict’s solution in a boiling tube, heat mixture for 5 mins
What colour should glucose change to to show its a reducing sugar?
Orange
