carbohydrates

• made up of carbon, hydrogen and oxygen
• monosaccharide 


  = a single sugar unit

  • maltose= alpha glucose+ alpha glucose
  • sucrose= glucose+ fructose
  • lactose= glucose+ galactose
• disaccharide 


  = 2 monosaccharides joined together by a condensation reaction.
• alpha glucose

  
• beta glucose

  
• condensation reaction 


  = forming 2 monosaccharides together

  • glycosidic bond

  A) glycosidic bond

  
• hydrolysis reaction 


  = breaking two monosaccharides apart.

  
• starch

  -monosaccharide= alpha glucose

  • bonding+ structure= hundreds of alpha glucose molecules joined by glycosidic bonds.
  • amylose= 1-4 bonds to form a long chain which forms a helix held by hydrogen bonds.
  • amylopectin= 1-4,1-6 bonds forms a branched structure- use= energy store for respiration, storage molecule of plants
• Glycogen 


  -monosaccharide= alpha glucose

  • structure+ bonding= 1-4,1-6 bonds, lots of branches, compact
  • use= glucose storage molecule
• cellulose 


  -monosaccharide= beta glucose

  • beta glucose bond together by a glycosidic bond in a condensation reaction- forms a linear chain, to form a molecule of cellulose
  • hydrogen bonds form between the hydrogen and oxygen from different molecules.
  • when joining 2 molecules together it's unstable so the second molecule has to be flipped to create a linear chain.
• testing for reducing sugars 


  = Benedict's reagent

  • gently heat
  • brick red precipitate formed
• testing for non-reducing sugars


  -Don't react with benedict's reagent and will give negative result.

  • boil with dilute hydrochloric acid
  • then it will give a positive brick red precipitate when benedict's reagent is added.
• testing for starch 


  =iodine test

  • purple/black colour if starch is present.