Tests for digestive products
a mind map of various tests that you are often asked to recall in exams in a simple format
- Created by: Tiff
- Created on: 16-12-12 19:24
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- Tests - digestive products
- Lipids
- shake thoroughly
- 2cm^3 sample + 5cm^3 ethanol --> test tube
- + 5cm^3 water + shake gently
- take comp. dry + grease-free test tube
- cloudy white colour = lipid present
- as a control, repeat with water instead of sample, final soln. should remain clear.
- Protiens, "biuret test"
- add few drops of v. dilute copper (II) sulphate soln. + mix gently
- add an equal amount of liquid sample and NaOH soln. --> test tube
- colour change blue --> purple = protien present
- Non-Reducing Sugars (disaccharides)
- place in gently boiling water bath, 5 mins; any dissacharides would be hydrolysed
- add equal amounts of another sample (l) to dilute HCL
- slowly add some sodium hydrogencarbonate soln. (neutralises HCL, check with indicator paper)
- first do test for reducing sugars, if none present:
- retest the soln, by heating with 2cm^3 Benedicts' reagent (wouldn't work in acidic conditions) in gently boiling water bath, 5 mins.
- if a non-reducing sugar was present the colour will turn orange/brown
- Starch
- add 2 drops iodine soln. + shake/stir
- 2cm^3 sample --> test tube if liquid, --> spotting tile if solid
- colour change brown --> blue-black if starch present
- Reducing Sugars (monosaccharides). "Benedicts' test"
- Add equal amounts of sample (liquid) + Benedicts' reagent --> test tube
- heat in gently boiling water bath, 5 mins
- if colour change blue --> red/brown, a reducing sugar is present. (it's a semi-quantitative test because degree of colour change depends on conc. of reducing sugar)
- Non-Reducing Sugars (disaccharides)
- place in gently boiling water bath, 5 mins; any dissacharides would be hydrolysed
- add equal amounts of another sample (l) to dilute HCL
- slowly add some sodium hydrogencarbonate soln. (neutralises HCL, check with indicator paper)
- first do test for reducing sugars, if none present:
- retest the soln, by heating with 2cm^3 Benedicts' reagent (wouldn't work in acidic conditions) in gently boiling water bath, 5 mins.
- if a non-reducing sugar was present the colour will turn orange/brown
- Lipids
- Reducing Sugars (monosaccharides). "Benedicts' test"
- Add equal amounts of sample (liquid) + Benedicts' reagent --> test tube
- heat in gently boiling water bath, 5 mins
- if colour change blue --> red/brown, a reducing sugar is present. (it's a semi-quantitative test because degree of colour change depends on conc. of reducing sugar)
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