1.2- Carbohydrates - monosaccharides

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  • Created by: Megan2413
  • Created on: 15-07-17 10:33
What is the general formula for a monosaccharide?
(CH2O)n
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Give three examples of monosaccharides
- Glucose - Galactose - Fructose
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What are the two isomers of glucose?
- alpha - beta
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Are all monosaccharides and some disaccharides reducing or non-reducing sugars?
Reducing sugars
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What is a reducing sugar?
One which has the ability to reduce another chemical (donate electrons to)
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Which substance does a reducing sugar donate electrons to in its food test?
Benedict's reagent
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How is the Benedict's test carried out?
- Add 2cm3 of the sample to a test tube - Add 2cm3 of benedict's reagent to the test tube - Gently boil in water bath for five minutes
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What shows the presence of a reducing sugar in this test?
The solution turns orange-brown
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What is benedict's reagent made up of?
Copper (II) sulfate
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When benedicts reagent is reduced what happens in chemical terms?
Copper (II) sulfate is reduced to an insoluble red precipitate of Copper (I) oxide
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What is the colour sequence a reducing sugar undergoes in the benedict's test?
Blue > Green > Yellow > Orange > Red
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How can this colour change give us semi-quantitative data?
The colour of the reducing sugar after heating with benedict's reagent can show us the concentration of reducing sugar present, hence the further along the colour change the higher the concentration of reducing sugar
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Why is this a semi-quantitative and not a quantitative analysis?
It is an approximation of the quantity of a substance, not an accurate quantity
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Other cards in this set

Card 2

Front

Give three examples of monosaccharides

Back

- Glucose - Galactose - Fructose

Card 3

Front

What are the two isomers of glucose?

Back

Preview of the front of card 3

Card 4

Front

Are all monosaccharides and some disaccharides reducing or non-reducing sugars?

Back

Preview of the front of card 4

Card 5

Front

What is a reducing sugar?

Back

Preview of the front of card 5
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