611181
Description
Mind Map by m.c.ridley, updated more than 1 year ago
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Created by m.c.ridley
about 11 years ago
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Biological molecules: chemical tests
- Starch test
- Iodine - goes blue/black
- Iodine - goes blue/black
- Sugars
- Reducing sugar = monosaccharide like glucose.
Non-reducing sugar = disaccharide like sucrose
- Reducing sugars - Add Benedict's solution. Heat to 80'C in a water bath - gives orange/red precipitate
- Non-reducing sugars - do test for reducing sugars first. If you get no result,
repeat by boiling with HCl. Add sodium hydrogencarbonate to neutralise then
repeat test. Will go to an orange/red precipitate if non-reducing sugars were in original
sample.
- Estimating amount of sugar in an unknown. Set
up a control where you do the test with solutions
of known sugar concentration. Time how long it
takes to get an orange precipitate. Repeat with
the unknown and compare to estimate its
concentration.
- Reducing sugar = monosaccharide like glucose.
Non-reducing sugar = disaccharide like sucrose
- Protein test - add Biuret reagent. Goes from blue to lilac.
- Lipid - Add ethanol to unknown. Shake. Pour into a new test tube
containing water. If unknown contains lipid, a white emulsion will fform
on top of the water.
- Colorimeter - to work out
concentration of sugar. Do
Benedict's test. Pour some of
the precipitate from the
completed test into a
centrifuge tube. Centrifuge to
ensure the precipitate goes to
the bottom of the tube.
Pipette off some of the liquid
on top - put into a cuvette.
Place cuvette into a
colorimeter - the higher the
concentration of glucose, the
more copper sulphate will
have reacted so the greater
the % transmission reading.
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