Carbohydrates

• The monomer of carbohydrates is monosaccharides
• glucose , galactose and fructose are all isomers
• isomers are two or more compounds with the same formula but a different arrangement of atoms in the molecule and different properties
• alpha glucose has h atom on top and hydroxyl group at the bottom
• beta glucose has h atom on the bottom and hydroxyl group on top
• disaccharides means two sugars
• glycosidic bond : a condensation reaction between two monosaccharides
• glucose + glucose = maltose

  glucose + galactose = lactose

  glucose + fructose = sucrose
• Polysaccharides :

  
  

  Starch

  Glycogen

  Cellulose
• alpha-glucose + alpha-glucose = maltose

  
  

  maltose = Starch
• Starch has two different structural forms :

  
  

  Amylose and Amylopectin
• Amylose : linear molecule consists of 1-4 linkages only
• linkages mean where the glycosidic bond is formed
• Amylopectin- same linear base as amylose but with the additional secondary chain that has 1-6 linkages
• Glycogen can be found in animal and fungi cell
• Glycogen is also made from alpha glucose and alpha glucose
• glycogen’s structure is like amylopectin but has repetitive branching every 10 glucose molecules instead of 20
• properties of starch and glycogen:

  
  

  1. compact
  2. insoluble
  3. branching
• Compact : large volumes stored in small spaces , great storage molecules
• insoluble : no osmotic effect on the cells , beneficial as no water can enter and damage the cell
• branching : branched structure allows for fast hydrolysis of polymers into glucose
• the three hexose monosaccharides :

  • glucose
  • galactose
  • fructose
• glucose , fructose and galactose have the molecular formula : C6 H12 O6
• when monosaccharides react a glycosidic bond is formed
• name three disaccharides :

  • maltose
  • sucrose
  • lactose
• maltose , sucrose , and lactose all hav the molecular formula : C12 H22 O11
• alpha glucose has hydroxyl group at the bottom ( HOH)
• beta glucose has the hydroxyl group at the top (OHH)
• starch is the storage polymer of alpha glucose in plant cells
• starch is insoluble
• when starch is made from amylose it has 1,4 glycosidic bonds
• when starch is made for amylopectin it has 1,4 and 1,6 glycosidic bonds
• glycogen is the main storage polymer of alpha glucose in animal cells
• glycogen has 1,4 and 1,6 glycosidic bonds
• cellulose is a b-glucose gives rigidity to plant cell walls
• cellulose has 1,4 glycosidic bonds
• cellulose is a straight-chain , unbranched moleucle
• in cellulose , alternate glucose molecules are rotated 180 degrees
• in cellulose , H-bond crosslinks between parallel strands which form microfibrils
• microfibrils mean high tensile strength