Carbohydrates

• The 3 monosaccharides


  Glucose, fructose and galactose
• The 3 disaccharides

  Sucrose, maltose and lactose
• The 3 polysaccharides


  Starch, cellulose and glycogen
• Monosaccharides 


  Single, simple sugars

  Pentoses ( 5 C )

  Hexoses ( 6 C )
• Glucose structure


  Monosaccharide, hexose sugar (C5H10O5), alpha glucose = monomer of starch and glycogen, beta glucose = monomer of
• Glucose function/ properties


  Primary respiratory substrate, so makes ATP - water soluble (polar) affects osmotic water potential of solutions cells and organelles
• Disaccharides


  Condensation of 2 monosaccharides, held together by 1-4 glycosidic bonds
• Lactose.


  alpha glucose + galactose
• Maltose


  Alpha glucose + alpha glucose
• Sucrose


  Alpha glucose + fructose
• Starch structure


  Alpha glucose, amylose = 1-4 glycosidic bonds and a helical structure, amylopectin = 1-4 and 1-6 glycosidic bonds and a branched structure
• Starch function


  Energy storage - releases alpha glucose, primary respiratory substrate for making ATP
• Starch structure → function


  Helical /branched so compact so large molecules can't leave cell, insoluble in water so no osmotic effect
• Starch location

  Plant cells → chloroplasts (starch grains)
• Glycogen structure


  Alana glucose, 1-4 glycosidic bonds and lots of 1-6 glycosidic bonds, very branched
• Glycogen function


  Energy storage, releases alpha glucose, primary substrate for making ATP
• Glycogen structure → function


  Branches create more ends for faster hydrolysis to release more glucose.
• Glycogen location


  Animal cells - muscle + liver cells
• Cellulose structure


  Beta glucose, only 1-4 glycosidic bonds, beta glucose is inverted 180°, straight chains and , hydrogen bonds when bundles form microfibres or macrofibrils
• Cellulose function


  Mechanical support and turgor pressure.
• Cellulose structure → function

  Cross links between straight and unbranched chains makes strong and rigid fibres
• Cellulose location


  Plant and algae cell walls
• Biochemical test for starch 


  Add iodine, will go from orange to blue/black if starch is present
• Biochemical test for reducing sugar (monosaccharides)


  Add benedict’s solution, heat up, will go from blue to brick red

  precipitate
• Biochemical test for non-reducing sugars ( sucrose, polysaccharides )


  Boil in acid to hydrolyse glycosidic bonds releasing monosaccharides, add alkali to neutralise, follow with test for reducing sugars