Carbohydrates

• Carbohydrates = organic compound containing Carbon, Hydrogen, Oxygen
• Monosaccharide = small organic molecules, basic unit/building blocks for larger carbohydrates
• Two monsaccharide form a disaccharide, multiple are polysaccharides
• General formula for carbohydrate = (CH2O)n, - ose
• Alpha glucose - Hydrogen is above the ring

  Beta glucose - Hydrogen is below the ring
• What does the addition of glucose form?

  Glycosidic bond (1,4) and water
• What reaction is used to form polysaccharides?

  Condensation reaction
• What reaction is used to break up polysaccharides?

  Hydrolysis
• Maltose = alpha glucose + alpha glucose

  Sucrose = alpha glucose + fructose

  lactose = alpha glucose + galactose
• Sucrose = C12H22O11

  Fructose = C5H10O5

  Galactose = C6H12O6
• Functions of monosaccharide:

  • source of energy in respiration -> bonds broken to release energy which is transferred to make ATP
  • building block for larger molecules
  • intermediate in reactions
  • structural (carbohydrates)
  • soluble in water
• amylose = linear, unbranched molecule with alpha 1,4 glycosidic bonds forming between C1 on one glucose monomer and C4 on and adjacent glucose monomer
• Amylopectin = branched chains of glucose monomers joined with alpha-1,4 glycosidic bonds, cross linked with alpha-1,6 glycosidic bonds

  
• Glycogen = main storage product in animals

  • have a-1,4 and a-1,6 glycosidic bonds but have shorter a-1,4 linked chains and they are more branched
• Functions of starch:

  • insoluble -> have no osmotic effect
  • cannot diffuse out of the cell
  • Compact molecule -> can be stored in small places
  • carries lots of energy in its C-H and C-C bonds

  Makes it good for storing glucose
• Cellulose - a polysaccharide made of beta glucose, that are joined by beta-1,4 alpha glycoside bond, where the beta links rotate adjacent by 180° -> allows hydrogen bonds to form between OH groups
• Adjacent parallel chains contributes to celluloses stability
• Microfibrils = 60/70 cellulose molecules become tightly cross-linked to form bundles, called fibres
• Cellulose fibre:

  • several layers that run parallel within a layer, angled at adjacent layers
  • laminated structure contributed to strength of cell
  • freely permeable-> spaces between fibres
  • water and solutes can penetrate through these spaces in cell wall to cell membrane
• Chitins = found in exoskeleton of insets and in fungal cell walls
• Chitin resembles cellulose with beta-1,4 linked monomers

  monomers are rotated 180° in relation to neighbours
• Chitin technically not a carbohydrate as it has nitrogen containing groups
• Monomers = individual structurally-similar subunits
• Polymers = several monomers combined to form larger units
• Isomer = molecules with the same molecular formula but atoms are arranged differently
• Benedicts test for reducing sugar:(sucrose)

  • heat up solution
  • Blue -> brick red means present
  • green = some traces
  • orange = moderate levels
  • better than the biuret test as it has more information
• Properties of glycogen:

  • coils into compact molecules -> allows large quantity to fit into small spaces available
  • lows solubility in water -> doesn’t influence water potential -> essential for storage
  • Highly branched -> enables rapid hydrolysis of molecule -> rapid access to glucose for respiration
• Test for non-reducing sugars:

  • mix solution with equal volume of Benedict’s reagent
  • heat mixture in a water bath
  • solution will remain blue if reducing sugar isn’t present
  • put test solution into a boiling tube and add few drops of hydrochloric acid and heat in a water bath
  • add few drops of sodium hydroxide and add Benedict’s reagent, heat mixture in water bath
  • blue -> orange/ red then non-reducing sugar is present
• Test for starch:

  • mix solution with few drops of iodine in potassium-iodide solution
  • if starch is present, solution will change to blue/black