Biological molecules : Cabohydrates

?
View mindmap
  • Biological Molecules: Carbohydrates
    • Carbohydrates = carbon + water
    • The making of large molecules
      • Monomer - individual molecules that form chains
      • Polymers - monomers that join together
    • In carbohydrates, the basic unit is sugar (saccharide)
      • Monosaccharide - A single monomer
        • General Formula (CH2O)n where n can be any number from three to seven
        • Examples of monosaccharides ; Glucose C6H12O6 ,Galactose and fructose
      • Disaccharide - A pair of monosaccharides
    • Testing for non reducing sugars
      • Reducing Sugars - Is a sugar that can donate electrons to (or reduce) another chemical
      • Method - 1) Add 2cm3 of the food sample to be tested to a test tube. If the sample is not already in liquid form, first grind it up in water. 2) Add an equal volume of benedict's reagent 3) Heat the mixture in a gently boiling water bath for five minutes 4) If reducing sugar is present solution turns orange - brown
      • Colour Change - Blue = no reducing sugar present ,  green = very low, yellow = low, orange = medium , red = high concentration
    • Disaccharides
      • Glucose + Glucose = Maltose
      • Glucose + Galactose = Lactose
      • Condensation Reaction - When the monosaccharides join a molecule of water is removed
      • Glucose + Fructose = Sucrose
      • Hydrolysis - When water is added to a disaccharide under suitable conditions, it breaks down glyosidic bonds and releases the constituent monosaccharides
    • Test for non reducing sugars
      • 1) If the sample is not already in liquid form, it must be ground up in water.
      • 2) Add 2cm3 of the food sample being tested to 2cm3 of benedicts reagent in a test tube a filter
      • 3) Place the test tube in boiling water bath for five minutes. If the solution doesn't change colour that means that there is no reducing sugars present
      • 4) Add another 2cm3 of the food sample to 2cm3 of dilute HCL in a test tube and place the test tube in boiling water for five mins (The dilute HCL will hydrolyse any disaccharide present into its constituent monosaccharides
      • 5) Slowly add some sodium hydrogen carbonate solution to the test tube in order to neutralise the HCL ( Benedicts reagent wont work in acidic conditons ) Test the pH paper to check that the solution is alkaline
      • 6) Retest the resulting solution by heating it with 2cm3of benedict's reagent in boilng water for five mins
      • 7) If an non reducing sugar was present in the original sample, the benedicts reagent will now turn orange - brown . This due to the reducing sugars that were produced form the hydrolysis of non reducing sugars

Comments

No comments have yet been made

Similar Biology resources:

See all Biology resources »See all Biological molecules resources »