Biochemical tests Flashcards
what does the benedict’s test for?
reducing and non-reducing sugars
how does the benedict’s test work for reducing sugars
1- place the sample to be tested in a boiling tube and add an equal volume of benedicts reagent
2- heat the mixture gently in a water bath
If reducing sugars are present, they will react with the copper ions in the reagent, reducing them from blue ions to red ions. this forms a brick red precipitate
how does benedicts test work for non-reducing sugars
if the non-reducing sugar is first boiled with hydrochloric acid, it will then give a positive result when warmed with benedicts solution, forming a brick red precipitate
what does the iodine test for?
starch
how does the iodine test for starch work?
iodine dissolved in potassium iodide solution are mixed with a sample
if the solution changes from yellow/brown to blue/black then starch is present
what is a colorimeter
it is a piece of equipment used to quantitatively measure the absorbance or transmission of light through a coloured solution.
the more concentrated a solution the more light it will absorb and the less light it will transmit.
what are biosensors
biosensors use biological components to determine the presence and concentration of molecules such as glucose.
consists of :
- molecular recogniton
- transduction
- display
what does the emulsion test for?
lipids
how does the emulsion test
1- sample is mixed with ethanol
2-resulting mixture is mixed with water and shaken
if a white emulsion forms as a layer on top of the solution this indicates the presence of a lipid.
what does the biuret test for
proteins
how does the biuret test work
1- add sodium hydroxide to the sample
2- add a few drops of copper sulfate solution to the sample
if a colour change from blue to lilac takes place then protein is present
what is chromatography
it is a technique that can be used to separate a mixture into its individual components
it relies on differences in the solubility of the components
what are two phases in chromatography
mobile phase and stationary phase
