3.1.2 - Carbohydrates

Thursday 14th September ‘23

Monosaccharides & Disaccharides

  • Monosaccharides: Sweet tasting; soluble; general formula: CH2On (n is between 3 and 7); Gluten, Galactose, Fructose

  • Glucose: Hexose sugar with two isomers. Alpha: Hydroxyl under the carbon ring; Beta: Hydroxyl above carbon ring.

  • Reducing sugars: Lactose and Maltose

  • Non-reducing sugars: Sucrose

  • Dissacharides: In glycosidic bonding, two monosaccharides join in a condensation reaction; Sucrose, Lactose, Maltose

Polysaccharides

  • Glycogen

    • Storage form of carbohydrates (excess glucose) in mammals.

    • Found in large quantities in liver and muscle cells.

    • Can be hydrolysed to release glucose quickly when it is needed for respiration.

    • Polymer of alpha glucose joined by 1,4 glycosidic bonds. It forms 1,6 glycosidic bonds at branch points.

  • Starch

    • Storage form of carbohydrates (excess glucose) in plants.

    • Insoluble but can be hydrolysed to release glucose for respiration.

    • Amylose - alpha glucose; 1,4 glycosidic bonds; unbranched (compact helix).

    • Amylopectin - alpha glucose; 1,4 glycosidic bonds; 1,6 glycosidic bonds at branches (every 25-30 molecules).

  • Cellulose

    • Storage form of carbohydrates (excess glucose) in plants.

    • Linked by hydrogen bonds to form a microfibril, macrofibril and cellulose fibre (forms cell walls)

    • Unbranched polymer of beta glucose which forms 1,4 glycosidic bonds by flipping.