monomers + polymers

• What are monomers?

  Smaller soluble molecules from which larger molecules are made
• What are polymers?

  Molecules made from a large number of similar monomers joined together
• What are examples of monomers?

  Monosaccharides (polysaccharides)

  Amino acids (polypeptides)

  Nucleotides (polynucleotide)
• What is a condensation reaction?

  Joins two molecules together with the formation of a chemical bond and involves the elimination of a molecule of water
• What is a hydrolysis reaction?

  Breaks a chemical bond between two molecules and involves the use of a water molecule
• What elements do carbohydrates contain?

  Carbon

  Hydrogen

  Oxygen
• What are monosaccharides?


  The monomers from which larger carbohydrates are made
• What are common monosaccharides?

  glucose, fructose, galactose
• When is a glycosidic bond formed?


  During a condensation reaction between 2 monosaccharides
• What are disaccharides?

  Two monosaccharides joined together by a glycosidic bond which forms during a condensation reaction
• glucose + glucose - >


  maltose + water
• glucose + fructose - >


  sucrose + water
• glucose + galactose - >


  lactose + water
• What are the two isomers of glucose?


  alpha glucose and beta glucose
• What is an isomer?

  Same chemical formula but a different structural formula
• Describe the difference between the two isomers of glucose


  The position of the hydrogen and hydroxyl groups on carbon 1 are inverted
• What are the common polysaccharides and the monosaccharides they are made from?

  Glycogen - alpha glucose

  Starch - alpha glucose

  Cellulose - beta glucose
• Describe and explain the difference in the structure of polysaccharide chains

  In the cellulose polymer, the monomers face in alternate directions rather than all the same way as it is in starch/glycogen.

  This is because starch and glycogen are polymers of alpha glucose whereas cellulose is a polymer of beta glucose.

  In beta glucose the position of the hydrogen and hydroxyl groups on carbon atom 1 are inverted.
• How is glycogen different from starch?

  Shorter chains

  More highly branched

  Larger surface area
• What are the reducing sugars?

  glucose, fructose, galactose, lactose and maltose
• Biochemical test for reducing sugars

  Add benedict's solution to sample

  Heat to 95C

  If reducing sugar is present, there will be a colour change from blue to orange/red
• What is the non reducing sugar?

  sucrose
• Biochemical test for non reducing sugars

  Do benedict's test and stays blue

  Boil a fresh sample with acid

  Then neutralise with alkali

  Heat with benedict's solution at 95C

  If non reducing sugar is present, there will be a colour change from blue to orange/red
• Biochemical test to identify starch

  Add iodine on potassium iodide solution to sample

  Colour from orange to blue/black if positive
• Suggest a way, other than comparing colour changes, in which different concentrations of reducing sugar could be estimated

  Filter and dry the precipitate in each sample

  Find the mass

  The higher the mass of the precipitate, the higher the reducing sugar is present
• How is glycogen similar to starch?

  Polymer of alpha glucose

  Coiled into a helix got compact storage

  Insoluble so it doesn't affect water potential
• Structure of starch


  - Coiled into a helix so it's compact so a lot can fit into a small space

  
  

  - Insoluble so it doesn't affect water potential

  
  

  - Large molecule so it doesn't diffuse across the cell membrane and out of cells

  
  

  - Branched which provides a larger surface area so it can be more rapidly hydrolysed so glucose can be released more rapidly for respiration for energy release
• Structure of glycogen


  - Coiled into a helix so it's compact so a lot can fit into a small space

  
  

  - Insoluble so it doesn't affect water potential

  
  

  - Polymer of a-glucose so easily hydrolysed

  
  

  - Highly branched
• Structure of cellulose


  - Long, straight and unbranched chains of B-glucose

  
  

  - linked together by many hydrogen bonds to form microfibrils

  
  

  - provide strength and rigidity to plant cell walls