as-u1-2.3 carbohydrates-disaccharides and polysaccharides

What’s the question? 1.Polymer

2.Monosaccharide

3.Red

Here's the answers, all you

have to do is write the

questions!

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Carbohydrates-Polysaccharides

Objective: To understand how monosaccharides form polysaccharides.

Outcomes: ~ Describe what a disaccharide is and name examples. ~ Explain how monosaccharides are linked to form polysaccharides.~ Explain how to carry out a test for non-reducing sugars and for starch.

Keywords

DisaccharidePolysaccharideCondensation reactionGlycosidic bondHydrolysis

Thursday 13 April 2023

DisaccharidesMonosaccharide + monosaccharide = disaccharide

Monosaccharide

Monosaccharide

Disaccharide

Glucose Glucose MaltoseGlucose Fructose SucroseGlucose Galactose Lactose

How?

glucose + glucosemaltose + water

Condensation reaction

Glycosidic bond

Test for non-reducing sugars (Sucrose)1.Confirm that the sample you’re

testing is not a reducing sugar.

2.Add 2cm3 of food sample (liquid form) to 2cm3 of dilute hydrochloric acid and place in a gently boiling water bath for 5mins.

3.Slowly add sodium hydrogen carbonate solution. Check the solution is then neutral.

4.Re-test this solution now again with Benedict’s.

Test for non-reducing sugars (Sucrose)Hydrochloric acid is added to the sample because…

Sodium hydrogencarbonate is added because…

If a non-reducing sugar is present, the Benedict’s reagent will now turn red because…

PolysaccharidesPolymers.

Large molecules yet compact.

Insoluble.

e.g. Starch

Hydrolysed into glucose.

Starch granules in plant cells

e.g. Cellulose

Provides structural support in plant cells.

Test for starch1.Add two drops

of sample onto a spotting tile.

2.Add two drops of potassium iodide.

3.Starch indicated by blue-black result.

2.3 Carbohydrates-disaccharides and polysaccharidesForming and breaking glycosidic bonds

Complete the diagrams below to show how glycosidic bonds can be formed and broken.

This type of reaction is called a…The molecule formed is…

This type of reaction is called a… The molecules formed are…