sugars

• what is the name of the bond that forms between 2 monosaccharides

  disaccharide
• what molecule is released during a condensation reaction between 2 monosaccharides

  water
• what bond forms between the 2 monosaccharides as a molecule of water is released

  glycosidic bond
• what monosaccharide make up the disaccharide

  • maltose - alpha glucose
  • sucrose - glucose and fructose
  • lactose - glucose and galactose
• describe how to test for reducing sugars and say what a positive and negative result would look like

  1. heat sample with benedicts reagent
  2. if sample stays blue there is no reducing sugar present but if there is orange/ brick red then reducing sugar is present
  3. heat a new sample with dilute hydrochloric acid then neutralise sample by adding hydrogencarbonate. heat sample with benedicts regeant
  4. blue=no sugar presents brick red/orange= non-reducing sugar present
• what is a polysaccharide

  are polymers containing many monosaccharides linked by glycosidic bonds. like disaccharides, polysaccharides are formed by condensation reactions
• polysaccharides are mainly used as an energy store and as structural components of cells
• the major polysaccharides are starch and cellulose in plants and glycogen in animals
• Structure of starch

  constructed of 2 different polysaccharides:

  • amylose (10-30%)
  • amylopectin (70-90%)
• starch is the major carbohydrate storage molecule in plants
• starch is usually stored as intracellular starch grains in organelles called plastids
• plastids include green chloroplasts and colourless amyloplasts
• starch is produced from glucose made during photosynthesis. it is broken down during respiration to provide energy and is also a source of carbon for producing other molecules
• what is the test for starch

  iodine test
• what is cellulose

  cellulose is a polysaccharide and is the main part of plant cell walls. it is the most abundant organic polymer
• unlike starch, cellulose is very strong, and prevents cells from bursting when they take in excess water
• cellulose consists of long chains of beta glucose molecules joined by beta 1-4 glycosidic bonds
• the glucose chains form rope-like microfibrils, which are layered to form a network
• what is glycogen

  animals do not store carbohydrate as starch but as glycogen
• glycogen has a similar structure to amylopectin containing many alpha 1-6 glycosidic bonds that produce an even more branched structure
• glycogen is less dense and more soluble than starch, and is broken down more rapidly. this indicates the higher metabolic requirements of animals compared with plants