Carbohydrates - Disaccharides and polysaccharides

Joe Gundel
Mind Map by , created over 5 years ago

Mind Map on Carbohydrates - Disaccharides and polysaccharides, created by Joe Gundel on 02/02/2014.

Joe Gundel
Created by Joe Gundel over 5 years ago
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Carbohydrates - Disaccharides and polysaccharides
1 Glucose linked to fructose forms sucrose
2 Glucose linked to galactose forms lactose
3 Glucose linked to glucose forms maltose
4 When monosaccharides join together, water is removed, this is known as a condensation reaction
4.1 The subsequent bond that is formed is known as a glycosidic bond
5 When water is added to a disaccharide it breaks the glycosidic bond releasing the monosaccharides. This is known as hydrolysis.
6 Test for non-reducing sugars
6.1 some disaccharides are non-reducing sugars (e.g. sucrose)
6.2 They don't make Benedict's regent change colour
6.3 The sample must be in liquid form
6.3.1 If it is not, then grind it up with water
6.3.2 Add 2cm3 of the food to 2cm3 of Benedict's reagent in a test tube Place in test tube in a gently boiling water bath for 5 minutes If the solution does not change colour (remans blue) then a reducing sugar is NOT present Add another 3cm3 of the food to 2cm3 of hydrochloric acid in a test tube and place in a gently boiling water bath for 5 minutes The hydrochloric acid will hydrolyse any disaccharides present into its monosaccharides Slowly add sodium hydrogencarbonate solution to the test tube in order to neutralise the hydrochloric acid, check with pH paper to ensure the solution is alkaline Re-test the resulting solution by heating it with 2cm3 of Benedict's reagent in a gently boiling water bath for 5 minutes If a non-reducing sugar is present in the original sample, the Benedict's reagent will now turn orange-brown. This is due to the the reducing sugars that were produced from the hydrolysis of the non-reducing sugar
7 Polysaccharides are polymers formed by combining together many monosaccharides
7.1 Monosaccharides joined together by glycosidic bonds by condensation reaction
7.2 Very large molecules and so are insoluble
7.2.1 This makes them ideal for storage
7.2.2 When hydrolysed polysaccharides break down into disaccharides and monosaccharides
7.2.3 Polysaccharides, such as cellulose, are not used for storage, but for structural support
7.3 Starch is a polysaccharide
7.3.1 This is found in small grains E.g chloroplasts
7.3.2 Test for starch carried out at room temperature Place 2cm3 of the sample being tested into a test tube Or a few drops can be placed on a depression of a spotting tile Add two drops of iodine and shake/stir The presence of starch is indicated by a blue-black coloration

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