1.4 starch, glycogen cellulose

• Starch is made up of chains of alpha glucose monosaccharides. These chains can either be branched or unbranched.
• Unbranched chains are wound in a tight coil which makes the molecule very compact
• The main role of starch is energy storage
• Structure of starch:

  1. insoluble so water isn’t drawn into the cells
  2. large and insoluble so it doesn’t diffuse out of cells
  3. compact so a lot can be stored in a small space
  4. when hydrolysed, forms alpha glucose which is easily transported and used in respiration
  5. branched form has many ends which can be acted on by enzymes
• starch is found in plants whereas glycogen is found in animals
• glycogen is similar to starch but it has shorter chains and is more branched
• cellulose is made up of beta glucose
• cellulose has straight unbranched chains which are parallel to each other, allowing hydrogen bonds to form cross, linkages between adjacent chains
• cellulose molecules are grouped together to form microfibrils, which are arranged in parallel groups called fibres