1.2 - 1.3 Carbohydrates

1.2 - 1.3 Carbohydrates

1. Monomer

   • Polymer
     • Polysaccharide
   • Monosaccharide
     • Glucose
       • Hexose Sugar - C6H12O6
       • Isomers
         • a-glucose
         • b-glucose
     • Galactose
     • Fructose

2. Test For Reducing Sugars

   • Reduction - A chemical reaction involving the gain of electrons
     • Therefore a reducing sugar = donates electrons
   • BENEDICTS TEST
     • Alkaline solution of Copper (II) Sulphate
     • When HEATED with a reducing sugar, forms an insoluble RED precipitate

3. Disaccharides

   • Glucose + Glucose = Maltose
   • Glucose + Fructose = Sucrose
   • Glucose + Galactose = Lactose
   • Made in a CONDENSATION REACTION
     • Molecule of water MADE
     • Glycosidic Bond
   • Broken down in a HYDROLYSIS REACTION into original monosaccharides
     • Molecule of WATER ADDED

4. Test for Non-Reducing Sugars

   • Must be in solution
     • Add Benedict's regent and heat
       • No colour change
         • Reducing sugar not present
         • Add food sample to dilute HCl + heat
           • This will hydrolyse any disaccharide present into constituent monosaccharides
           • Add sodium hydrogencarbonate solution to neutralise acid
             • Benedicts doesn't work in acidic conditions
             • Test with pH paper
               • Re-test with Benedict's
                 • Heat
                   • If a non-reducing sugar present in original sample, Benedict's will turn orange/brown
                     • This is due to reducing monosaccharide's made from non-reducing disaccharide

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