Monosaccharides

• Monomers made up of a single sugar unit, their general formula is (CH_2O)n; they are sub-grouped according to the number of carbon atoms they contain
• The suffix -ose is used in naming eg glucose (most of the time)
• Monosaccharide: Triose

  Value of ‘n’ (how many sugars): 3

  Molecular Formula: C_3​H_6​O_3​

  Examples: Glyceraldehyde
• Monosaccharide: Pentose

  Value of ‘n’ (how many sugars): 5

  Molecular Formula: C_5​H_10​O_​5

  Examples: Ribose and deoxyribose
• Monosaccharide: Hexose

  Value of ‘n’ (how many sugars): 6

  Molecular Formula: C_6​H_12O_6

  Examples: Glucose, fructose, and galactose
• The -OH group is called a hydroxyl group (polar, reason monosaccharides are soluble in water), in the straight-chain form, all but 1carbon has an attached hydroxyl group
• The remaining carbon atom has a carbonyl group attached to it (C=O); carbonyl group can be ketone or an aldehyde, this is what makes monosaccharides reducing sugars
• Benedict’s test:

  • Reducing sugars give a positive test as they reduce the copper (II) sulphate to copper (I) oxide, this forms a brick-red precipitate
  • Positive test is a colour change from blue to brick red, green, or orange-brown; depends on the sugar concentration and how much red precipitate is formed
• Monosaccharide: Glucose

  Type: Hexose

  Main Role: Respiration - for energy reproduction
• Monosaccharide: Fructose

  Type: Hexose

  Main Role: Found in nectar and many fruits, its sweet taste attracts animals for pollination and seed dispersal
• Monosaccharide: Galactose

  Type: Hexose

  Main Role: Glucose forms part of lactose, an energy source for young mammals
• Monosaccharide: Ribose

  Type: Pentose

  Main Role: A component of an RNA+ATP
• Monosaccharide: Deoxyribose

  Type: Pentose

  Main Role: A component of DNA