Polysaccharides

• What's the iodine test? 

  • In a spotting tile add a few drops of sample 
  • add a few drops of potassium iodide 
  • If sample stays brown- no starch present 
  • If sample blue/black- indicates starch
• What do plants store excess glucose as?

  Starch
• How can starch be utilized by plants?

  It can break down to release glucose for energy
• What are the two polysaccharides that make up starch?


  Amylose and amylopectin
• What is the structure of amylose?

  Long, unbranched chain of alpha-glucose
• How does the structure of amylose benefit its function?

  Its coiled structure makes it compact for storage
• What is the structure of amylopectin?


  Long, branched chain of alpha-glucose
• Why are the branches in amylopectin advantageous?


  They allow enzymes to access glycosidic bonds easily
• What is a key property of starch regarding water solubility?


  Starch is insoluble in water
• How does starch affect water potential in cells?


  It doesn't cause water to enter cells by osmosis
• Function of cellulose? 

  • Made of long, unbranched chains of beta-glucose 
  • Form straight cellulose chains
  • Linked by hydrogen bonds to from strong fibres called micro fibrils- provides structural support for cells (cell wall) 
• What is a polysaccharide? 

  • Is a carbohydrate, large numbers of monomers 
  • Is formed when two or more monosaccharides are joined by condensation reactions 
  • can be broken down by hydrolysis reaction into monosaccharides 
• Function of glycogen? 

  • Glucose that is stored in animal cells 
  • Has many side branches so quick release of energy 
  • Very compact so good for storage