carbohydrates 1.1

• what are polymers

  molecules made from a large number of monomers joined together.
• 3 examples of polymers

  carbohydrates, proteins and nucleic acids
• what are monomers

  smaller units from which larger molecules are made
• 3 examples of monomers

  monosaccharides (glucose), amino acids and nucleotides
• what are carbohydrates made from

  monosaccharides
• what elements do all carbohydrates contain

  C, H, O
• what are monosaccharides

  monomers from which larger carbohydrates are made.
• examples of monosaccharides

  glucose, fructose, galactose
• what kind of sugar is glucose

  hexose

  = a monosaccharide with 6 carbon atoms in each molecule
• what are the 2 isomers of glucose

  alpha (α) and beta (β)

  
• what are isomers

  molecules with the same molecular formulas, but different structural formulas
• what's the difference between alpha and beta glucose molecule

  alpha glucose are disaccharides=alpha Habove C1

  beta glucose, cellulose=beta H isbelow C1

  
• 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 do condensation reactions join together

  2 monosaccharides which forms a glycosidic bond.
• how is a disaccharide formed

  When two monosaccharides join together
• what happens when monosaccharides are joined together

  a glycosidic bond forms between the two monosaccharides as a molecule of water is released

  
  

  - disaccharides are formed

  - formed by a condensation reaction
• how is maltose formed

  maltose is a disaccharide = glucose + glucose→maltose + water
• how is sucrose formed + what is it

  sucrose is a disaccharide = glucose + fructose → sucrose + water
• how is lactose formed + what is it

  lactose is a disaccharide = glucose + galactose → lactose + water
• what is always a product of a condensation reaction

  water

  - remember to add onto your equation
• what is hydrolysis

  breaks the glycosidic bond between molecules using a water molecule

  = opposite to condensation
• how are polymers broken down into monomers

  hydrolysis reactions
• what can all sugars be classified as

  Reducing or non-reducing
• what is sugar a general term for

  saccharides
• what does the Benedictus test for

  sugars
• how to test for reducing sugars

  1. add Benedictus reagent (blue) to a sample + heat It in a water bath at 80 degrees for 5 minutes

  2. if the test is positive it will form a coloured precipitate

  
• what does the different precipitates mean about the amount of reducing sugar

  blue - none

  green - very low

  yellow - low

  orange - medium

  red - high
• what is benedicts reagent

  copper (II) sulfate
• why should you always use excess of Benedict solution

  to make sure that all the sugar reacts
• what are reducing sugars

  All monosaccharides

  = glucose, fructose, galactose

  
  

  AND some disaccharides

  = maltose + lactose
• what is a precipitate


  A solid that forms from a solution during a chemical reaction.
• what may suggest that a sugar is non reducing

  if the Benedict test comes back as negative (blue)
• how to test for non reducing sugars

  hydrolysis followed by Benedicts test

  
  

  1. break them down into monosaccharides by adding dilute HCL + carefully heating it in a water bath for 5 minutes to break glycosidic bond

  
  

  2. Neutralise it with sodium hydrogen carbonate

  
  

  3. test with PH paper to check solution is alkaline

  
  

  4. carry out the Benedict test as you would for reducing sugar

  
  

  5. if test is positive it will form a coloured precipitate - if the test is negative so stays blue it means there is no sugar present
• examples of non reducing sugars

  sucrose

  = all polysaccharides
• how is a polysaccharide formed

  formed by condensation reactions between many glucose monomers
• structure + function of starch

  - helical shape (amylose) held together by hydrogen bonds

  = compact so lots of glucose can be stored in a small volume (efficient energy storage)

  
  

  - insoluble

  = doesn't affect water potential

  = water not drawn in by osmosis

  
  

  - large

  = cant diffuse out of cell

  
  

  - hydrolyses to form alpha glucose

  = readily used in respiration

  
  

  - branches form with many ends (amylopectin)

  = can be acted on by enzymes simultaneously so glucose molecules are rapidly released

  = used for respiration
• what is starch + where can it be found

  a store of excess glucose which is broken down when a plant needs more glucose for energy

  
  

  - chloroplast
• what is starch a mixture of

  Two polysaccharides of alpha-glucose:

  - amylose

  - amylopectin
• amylose

  - long, unbranched chain of alpha glucose

  - angles of glycosidic bonds give it a coiled structure making it compact and good for storage.

  - it has has 1-4 glycosidic bonds
• amylopectin

  - long, branched chain of alpha glucose

  - its side branches allow the enzymes that break down the molecule to get at the glycosidic bonds easily

  = glucose can be released easily

  - 1-4 and 1-6 glycosidic bonds