Simple carbohydrates - monosaccharides and disaccharides

• what is alpha glucose structure?

  CH2OH

  6 | 5

  H /--------------O\ H

  | / \ |

  4|/ \| 1

  |\ OH / |

  | \ | | / |

  HO \|--------------|/ OH

  |3 2 |

  | |

  H OH
• what is the B-glucose structure?

  CH2OH

  6|5

  H /------------------O\ OH

  | / \ |

  4 | / \| 1

  | \ OH H / |

  | \ | | / |

  HO \|-----------------| / H

  | 3 2 |

  H OH
• what is the difference between alpha glucose and beta glucose?

  the H is above and the OH is below carbon 1 on alpha glucose whereas the H is below and the OH is above on beta glucose
• what are the properties of monosaccharides?

  • soluble in polar solvents
  • insoluble in non-polar solvents
  • classified by the number of carbon atoms
• how is the formulae of monosaccharides calculated?

  C(n)H(2n)O(n)
• what type of monosaccharide has 3 carbon atoms?

  Triose (e.g. glyceraldehyde)
• what type of monosaccharide has 5 carbon atoms?

  Pentose (e.g. ribose)
• what type of monosaccharide has 6 carbon atoms?

  Hexose (e.g. glucose, galactose)
• what are monosaccharides used for?

  • energy (respiration) - to generate ATP
  • components for larger molecules
• what isomers can glucose exist as?

  beta-glucose and alpha-glucose
• what is the difference between ribose and 2-deoxyribose?

  ribose is a pentose sugar and has a oxygen molecule on carbon 2 whereas 2-deoxyribose is a major DNA component which doesn't have an oxygen on its carbon 2 - just a hydrogen
• how are disaccharides formed?

  formed when two monosaccharides are joined by a glycosidic bond in a condensation reaction
• what are examples of disaccharides forming?

  • alpha-glucose + alpha-glucose -> maltose + water
  • alpha-glucose + beta-glucose -> lactose + water
• what are disaccharides used for?

  • energy (respiration)
  • components for larger molecules
• how can a disaccharide be formed from two monosaccharides?

  in a condensation reaction, the OH molecule on the carbon 1 of one alpha-glucose and the OH molecule on the carbon 4 of another alpha-glucose react to form water (H2O) and an Alpha-1, 4-glycosidic bond
• why can't the generic formula for monosaccharides be used for disaccharides?

  the water molecule was lost when the glycosidic bond was formed
• how is respiration controlled?

  is a multi-stage process, each catalysed by specific enzyme
• which type of glucose can plants and animals respire?

  alpha-glucose
• what does ATP stand for?

  Adenosine Triphosphate
• what are the components of ATP?

  • 3 phosphate groups connected by a high-energy bond (which breaks to release energy)
  • ribose
  • adenine
• what type of sugar are ribose?

  pentose sugar - composed of 5 carbon atoms
• how is ATP used as an energy store?

  High-energy bond between phosphate groups break to release energy
• what is the structure of amylose?

  • formed from alpha glucose joined by alpha-1, 4-glycosidic bond
  • unbranched
  • helix/coiled structure
• what are features of amylose?

  • used for energy store
  • insoluble so doesn't affect water potential of cell (or float away)
  • found in plants only
• what is the structure of amylopectin?

  • formed from alpha-glucose-1, 4-glycosidic bonds and alpha-1, 6-glycosidic bonds
  • forms a helix/coiled structure
  • highly branched
• what are features of amylopectin?

  • used for energy store
  • insoluble so doesn't affect water potential of cell (or float away)
  • branched so is more compact than amylose - better for storage
  • found in plants only
• what is the structure of glycogen?

  • highly branched
  • forms a coiled/helix shape
  • monomers joined by alpha-1, 4-glycosidic and alpha-1, 6-glycosidic bonds
• what are the features of glycogen?

  • insoluble
  • very compact (highly branched)
  • hydrolysed quickest
  • found in animals only
• why is it important for simple carbohydrates to be highly branched?

  can be more compact if it is highly branched - which is better for storage and animals can therefore store more energy (more glycogen)
• how does the iodine test for starch work?

  • starch-iodine complex which is formed as charge is transferred between the starch and iodine ions (tri-iodide and pentaiodine)
  • transfer of charge between starch and iodine ions changes space between energy levels
  • resulting in starch-iodine complex absorbing light at a different wavelength - resulting in an intense purple colour (blue/black)
• why are amylose and glycogen described as 'energy stores' whereas alpha-glucose is an 'energy source'?

  alpha-glucose is the soluble energy source, but when not needed it needs to be stored (amylose/glycogen). These are made up of the monomer alpha-glucose, but are insoluble so will be able to store energy until needed - alpha-glucose can't do this
• how is a glycosidic bond formed?

  condensation reaction
• what reaction and what enzyme breaks an alpha-glucose 1, 4-glycosidic bond?

  hydrolysis, amylase
• what reaction and what enzyme breaks an alpha-1, 6-glycosidic bond?

  hydrolysis, glucosidase