Unit 2 Section 1.4 Biochemical Tests for Molecules
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- Created on: 22-04-14 19:16
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- Biochemical tests for Molecules
- The Biuret Test for proteins
- if you need to find out if a substance contained proteins you would use the biuret test there are two stages to this test
- 1) - The test solution meeds to be alkaline, so first you add a few drops of sodium hydroxide solution
- 2) - Then you add some Copper Sulfate solution
- if protein is present, the solution turns purple.
- if nmo protein is present then the solution will stay blue
- 2) - Then you add some Copper Sulfate solution
- 2) - Then you add some Copper Sulfate solution
- if protein is present, the solution turns purple.
- if nmo protein is present then the solution will stay blue
- The Benedicts Test for Sugars
- all sugars can be classified as reducing or non reducing, to test for sugars you use the benedicts Test.
- the test differs depending on the type of sugar you are testing for
- Reducing Sugars
- include all monosaccharides and some disaccharides
- You add benedicts reagent to a sample and heat it
- if it tests positive it will form a coloured precipitate
- You add benedicts reagent to a sample and heat it
- include all monosaccharides and some disaccharides
- Non Reducing Sugars
- if the result of the reducing sugars test is negative, there could still be a non reducing sugar present
- to test for non reducing sugars, first you have to break them down into monosaccharides.
- to do this you take a new sample and boil it with dilute hydrochloric acid,
- then you neutralise it by adding sodium hydrogencarbonate
- Finally just carry out the benedicts test as you would for reducing sugar
- then you neutralise it by adding sodium hydrogencarbonate
- to do this you take a new sample and boil it with dilute hydrochloric acid,
- to test for non reducing sugars, first you have to break them down into monosaccharides.
- if the result of the reducing sugars test is negative, there could still be a non reducing sugar present
- Reducing Sugars
- the test differs depending on the type of sugar you are testing for
- all sugars can be classified as reducing or non reducing, to test for sugars you use the benedicts Test.
- The Iodine Test for Starch
- if you want to test for the presence of starch in a sample, you'll need to do the iodine test
- to test add iodine dissolved in potassium iodide to the test sample
- if there is starch present the sample changes from browny - orange to a dark, blue black colour
- if there is no starch present the sample stays browny - orange
- Emulsion Test for Lipids
- if you want to test for the presence of lipids in a sample, you will need to do an emulsion test
- To use this test, you shake the substance with ethanol for about a minute, then pour solution into water
- any lipid will show up as a milky emulsion
- if there is no lipid, the solution will stay clear
- To use this test, you shake the substance with ethanol for about a minute, then pour solution into water
- if you want to test for the presence of lipids in a sample, you will need to do an emulsion test
- The Biuret Test for proteins
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