Tests in biology

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Iodine Test for Starch
Firstly you add iodine dissolved in potassium iodide solution to the test sample.
If starch is present in the solution then the sample changes from brown/ orange to a dark
black/ blue colour
If there is no starch present then it should stay brown/ orange
Using the Biuret Test for Proteins
There are two stages involved in the Biuret test
The first stage is where a few drops of sodium hydroxide solution because the test
solution needs to be alkaline
Then copper(II) sulfate solution is added
If protein is present then a purple layer forms and if there is no protein then the solution
will say blue.
Using the Emulsion Test for Lipids
Firstly you shake the test substance with ethanol for about a minute and then pour the
solution into water
If lipid is present then the solution will turn milky
The more lipid there is, the more noticeable the milky colour will be
If there is no lipid present the in the solution then it will stay clear.


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