Carbohydrates

• Carbohydrates

  • organic ( high proportion of C atoms )
  • contains C , H O2
  • basic unit = monosaccharide
  • two mono = disaccharide
  • many mono = polysaccharide
• monosacharide

  • (CH2O)n N = no of C in molecule
  • triose sugar = 3 C
  • Pentose sugar = 5 C
  • hexose = 6 C eg glucose
• monosaccharide- hexose

  • formula = C6H12O6 but diff molecular structure
  • glucose = 2 isomers
  • alpha and beta based on positions of OH and A
  • diff forms = diff when they form polymers eg starch and glucose
• Alpha glucose

  
• beta glucose

  
• functions of monosaccharides

  • energy source in respiration , C-H and C-C bonds broke -> energy -> ATP
  • building block for larger molecules eg glucose used to make polysaccharides starch , glycogen and cellulose
  • intermediates in reactions eg trioses in respiration and photosynthesis
  • constituents of nucleotides eg deoxyribose in DNA , ribose in RNA , ATP and ADP
• disaccharides

  • 2 mono units joined w/ glycosidic bond and elimination of water = condensation

  
• Disaccharides

  • maltose = glucose + glucose -> germinates seeds
  • sucrose = glucose + fructose -> transport in phloem of flowering plants
  • lactose = glucose + galactose -> mammal milk
• Polysaccharides

  • large complex polymers -> v large no of monosaccharides = monomers linked by glycosidic bonds
• polysaccharides: glucose

  • main source of energy in cells
  • water soluble -> increase conc of cell contents + draws in water by osmosis but avoided by converting glucose into storage prodcut = starch
• polysaccharide: starch

  • insoluble = no osmotic effect
  • can’t diffuse out of cell
  • compact -> stored in small place
  • carries lot of energy in C-H and C-C bonds
  • main energy source in plants , found in high conc in seeds and storage organs like potato tubers
• polysaccharide: starch

  • made from alpha glucose bonded in 2 diff ways = amylose or amylopectin
• polysaccharides : amylose

  • linear , unbranded molecule
  • alpha-1,4-glycosidic bonds between C1 and C4 on diff glucose monomers = repeated = chain = coils into helix

  
• polysaccharide: amylopectin

  • chains of glucose monomers joined with alpha-1,4-glycosidic bonds
  • cross linked with alpha-1,6-glycosidic bonds = fit inside amylose
  • when glycoside bonds forms between C1 and C = side branch -> alpha-1,4-glycosidic bonds continue

  
• Polysaccharides: glycogen

  • Main storage product in animals
  • v similar to amylopectin
  • has alpha-1,4 and alpha-1,6 bonds but have shorter alpha-1,4 linked chains = more branched then amylopectin
• polysaccharide: cellulose

  • structural -> in cell walls -> most abundant organic molecule
  • long parallel chains of beta glucose joined by beta-1,4-glycosidic bonds and rotates 180 so H bonds can form between OH groups of adjacent parallel chains -> stability
  • between 60 and 70 = tightly cross linked = bundles = microfibrils
• polysaccharides: cellulose

  • cell wall = several layers of fibres -> run parallel within layer but at an angle to adjacent layers = lamiated structure = strong
  • cellulose fibres = freely permeable -> spaces between fibres
  • water and solutes = penetrate thru spaces in cell wall to cell membrane
• Polysaccharides: chitin

  • structural
  • in exoskeleton on insects and fungal cell walls
  • resembles cellulose -> long chains of beta-1,4-linked monomoers
  • has groups derived from amino acids added -> hetropolysaccharide
  • strong waterproof and light
  • also rotated 180 and long parallel chains = cross linked by H bonds = microfibrils