Carbohydrates contain the following elements; Carbon (C), Hydrogen (H), Oxygen (O)

  • Structure: Carbohydrates consist of simple sugars. General Formula: (CH2O)n , The ration of these elements is generally 1:2:1.
Types of carbohydrate Reducing sugars Soluble in water Example
Monosaccharides (1 sugar unit) Yes Yes Glucose C6H12O6(fruit e.g. grapes), fructose (honey, sweet fruits)
Dissacharides (2 sugar units joined together) Some dissacharides e.g. maltose, lactose (but not sucrose) Yes Sucrose (table sugar) lactose (milk), maltose (germinating seeds)
Polysaccharides No No Starch (bread, pasta, potatoes), cellulose (vegetables, wholemeal bread), glycog
  • Role of carbohydrates in cell structure and metabolism:
    • Cell structure: Cellulose forms the structure for plant cell walls, whilst Chitin forms the structure for fungi cell walls and exoskeleton of insects.
    • Metabolism:
      Catabolic reactions e.g. respiration

C6H12O6 + 6O2      ->    6CO2 + 6 H2O + Energy
         Anabolic reactions e.g. photosynthesis

6CO2 + 6 H2O   ->   C6H12O6 + 6O2

Energy storage: carbohydrates are stored in plants as starch & in animals (muscles and liver) as glycogen


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