Carbohydrates

• Monosaccharide definition

  one sugar unit
• Disaccharide definition:

  
  

  molecule of 2 sugar units chemically bonded together
• Polysaccharide definition:

  
  

  polymer of sugar monomers joined by glycosidic link
• Hydrolysis reaction:

  
  

  using water in a chemical reaction to break down a molecule
• Condensation reaction:

  
  

  where water is released as a product during a reaction
• 3 examples of monosaccharides

  glucose, fructose, galactose
• 3 examples of disaccharides

  sucrose, maltose, lactose
• glucose + glucose

  maltose
• fructose + glucose

  sucrose
• glucose + galactose

  lactose
• What is the glycosidic link?

  
  

  A covalent bond formed between two monosaccharides
• What shape is poly alpha glucose?

  Helix
• What shape is poly B glucose ?

  
  

  long straight chain
• What is the test for starch?

  Iodine test
• Describe the structure of starch:

  
  

  Starch is branched and forms a helix
• How are disaccharides formed?

  the condensation of 2 monosaccharides
• What are 2 reasons for starch's structure?

  
  

  1. makes molecules more compact, meaning there are many alpha glucose units in one place therefore it is a good store of energy

  2. branches increase the number of end points where enzymes can act to release glucose
• What is the difference between the structure of glycogen and starch, why?

  
  

  glycogen has more branching so glucose can be released faster for a faster rate of respiration
• What type of bond holds the helix in place?

  
  

  hydrogen bonds
• Describe the structure of cellulose:

  
  

  - long straight unbranched chain of polyBglucose

  - cellulose chains are bundled together
• Alpha glucose

  
• Beta glucose

  
• What is an isomer ?

  A molecule with the same chemical formula but different structural formula
• Is poly-a-glucose soluble or insoluble and why is this useful?

  -insoluble

  -has no osmotic effect, maintains water potential so water does not enter the cell through osmosis and cause it to burst
• What do poly-beta-glucose bundles form and what do these provide to the molecule?

  Microfibrils , provide rigidity and strength