A-Level Biology AQA Notes

3.1.2 Carbohydrates

Carbohydrates
  • Monosaccharides are the simplest carbohydrates, consisting of only one sugar molecule (e.g. Glucose, Fructose & Galactose).
  • Glucose is a hexose sugar with 2 isomers
Picture
  • Disaccharides are sugars that are composed of two monosaccharides joined together in a condensation reaction, forming a glycosidic bond.
Amylose
Value
Maltose
2 × α-glucose
Sucrose
α-glucose and fructose
Lactose
β-glucose and galactose
  • Polysaccharides are formed by many monosaccharides joined together.
    • Amylose, amylopectin (starch) is the main polysaccharide energy store in plants, is composed of α-glucose.
    • In animals, the polysaccharide energy store is called glycogen, composed of α-glucose.
    • Cellulose is a structural component of plant cell walls, composed of long unbranched chains of b-glucose.