1A.2 Carbohydrates

• name three polysaccharides.

  starch, glycogen, cellulose.
• what is a reducing sugar?

  a sugar that can donate electrons to other hydroxyl containing chemicals.
• what bond is formed between two monosaccharides?

  glycosidic bond.
• what is the name of the test for sugars?

  Benedict's test.
• what is the method for the benedicts test?

  • add excess copper ii suplate to a sample solution. • heat in a water bath.
• which disaccharides are reducing sugars?

  maltose and lactose.
• does the benedicts test identify reducing or non-reducing sugars?

  reducing sugars.
• glucose + fructose =


  sucrose.
• what reaction joins two monosaccharides together?

  condensation reaction.
• name three disaccharides.

  sucrose, lactose, maltose.
• which monosaccharides are reducing sugars?

  all of them.
• what happens to copper ii sulphate during a positive result of the benedicts test?

  it is reduced to copper i oxide.
• what are isomers?

  compounds with the same molecular formula but different structures/arrangement.
• what are the two isomers of glucose?

  alpha and beta.
• name three monosaccharides.

  glucose, fructose, galactose.
• what chemical is benedicts reagent?

  copper ii sulphate.
• what is a positive result of the benedicts test?

  a coloured precipitate formed. blue-green-yellow-red. low - high conc of reducing sugars.
• what safety hazards are present when carrying out the benedicts test?

  • copper ii sulphate is an irritant so wash hands and wear eye protection.• hot water can scold.
• how do we quantify results from the benedicts test

  
  

  filter, dry, weigh
• what is the test for non-reducing sugars?

  • add dilute HCL to sample and heat in water bath. • neutralise with sodium hydrogen carbonate (needs to be slightly alkali) • carry out benedicts test.
• why do we add HCL when testing for non-reducing sugars?

  to hydrolyse the glycosidic bond and expose the aldehyde/ketone functional group.
• A glucose + A glucose =

  Maltose
• Glucose + galactose =

  Lactose