Carbohydrates

• What are the roles of carbohydrates?

  • Energy supply for cells
  • Energy storage
  • Structural components
  • Cellular recognition
  • Building blocks for biological molecules
• Whats the main function of a monosaccharide?

  Energy source
• Whats the main function of disaccharides?

  • Transport form
• Whats the main function of polysaccharides?

  • Storage form
• What are the two isomers of gluecose?

  • alpha-gluecose
  • beta-gluecose
• What is different about the two isomers of gluecose?

  • In alpha-gluecose the OH group is located at the bottom of the carbon 1
  • In beta-gluecose the OH group is located at the top of the carbon 1
• What are the properties and uses of gluecose?

  • It is soluble - the OH group can form hydrogen bonds with water
  • Its bonds store a lot of energy - the energy is released when the bonds are broken
• Give 3 disaccharides and how theyre made?

  • Maltose = gluecose + gluecose
  • Sucrose = gluecose + fructose
  • Lactose = gluecose + galactose
• How are disaccharides formed and broken?

  • Theyre formed from condensation
  • Theyre broken from hydrolysis

  The reactions involve the formation or the breakdown of a covalent bond known as a glycosidic bond
• What are the 3 examples of polysaccharides?

  • Glycogen
  • Cellulose
  • Amylopectin / Amylose
• What are some qualities of starch?

  • Starch is an example of a polysaccharide used by plants to store excess glucose
  • This means that the starch can be hydrolysed back into gluecose when plants require energy
  • Starch is made up of alpha-gluecose monomers joined by glycosidic links
• What are some features of amylose?

  • Joined by 1-4 glycosidic bonds
  • The angle of these bonds cause the chain to coil into a helix to make a compact structure
• What are some features of amylopectin?

  • Long branched chain of alpha-gluecose joined by both 1-4 glycosidic links and 1-6 glycosidic bonds (formed by condensation reaction)
  • Its side branches allow enzymes to hydrolyse alpha-glucose monomers easily
• What are the functions of starch?

  • Insoluble - doesnt effect water potential so water cells dont enter by osmosis
  • Large - cannot diffuse out of cells
  • Many side branches
  • Coiled - compact so that a lot of glucose can be stored in a small space
  • Hydrolysis releases alpha-glucose monomers - readily used in respiration
• What are some features of glycogen?

  • Used by animals to store excess gluecose
  • Means that glycogen can be hydrolysed back into gluecose when animals require energy
  • Made up of 1-4 and 1-6 glycosidic bonds to form highly branched chains
• What are some functions of glycogen?

  • Insoluble - doesnt effect water potential
  • Compact - a lot of gluecose can be stored in a small space
  • More highly branched than starch
  • Large - it cannot diffuse out of cells
  • Hydrolysis release alpha-gluecose monomers - these rapidly used in respiration
• What is the features of cellulose?

  • Made from beta-glucose and is used for structural support for cell walls
  • When the two beta-gluecose monomers line up the OH groups dont line up so one of them has to flip 180 degrees so they align enough to react
  • When the beta-glucose join together to form long,straight unchained unbranched chains
  • The alternating inversion of the beat glucose allows for hydrogen bonds to form between individual chains
  • Great number of H bonds provides great strength to cellulose itself
• What happens when multiple cellulose chains tightly cross?

  • When they tightly cross via hydrogen bonds they form bundles called microfibrils
  • They microfibrils come together to make macrofibrils which combine to make strong cellulose fibres in the cell wall
• What are the adaptations of cellulose for its role?

  • Long, straight and unbranched chains - provide rigidity to cell wall
  • Hydrogen bonds - these cross link the chains to add collective tensile strength
  • Microfibrils - these provide additional strength