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Carbohydrates2011329191040 Powered By Docstoc
• Carbohydrates are         • Green plants contain a
                              special pigment called
  compounds made of           CHLOROPHYLL which traps
  Carbon, Hydrogen and        sunlight. Plants use this
  Oxygen.                     energy along with CO2 gas
                              and Water to make food –
• They are made in            Glucose (sugar), Oxygen is
  PHOTOSYNTHESIS              also released.
• This process is carried   • CO2 + H2O —>O2 + C6H12O6
  out in the leaves of      • Light and Chlorophyll must
                              be present for the reaction to
  Green Plants.               take place.
 Examples of Carbohydrates
• Carbohydrates contain the elements C.H. and O.
• There are twice as many H in the molecules as C and
• They can be split into 3 main groups: monosaccharides,
  disaccharides and polysaccharides.( saccharide =
  sugar group)
• Monosacharides – formula C6H12O6 e.g. glucose,
  fructose and galactose. They are isomers.
• Disaccharides – formula C12H22O11 e.g.. Lactose,
  maltose, sucrose. They are isomers
• Polysaccharides – (C6H10O5)n e.g.. Cellulose, starch,
• Respiration is when         • When we eat food the energy
  Carbohydrates are             trapped in the food is
  broken down to release
  energy. Oxygen must be      • We can show that energy is
                                contained in food in the lab.
                              • Example
• CO2 and H2O are             • Exploding custard tin.
  produced.                   • When we burn sugar in the
• C6H12O6 +O2 —>CO2 +           lab we can test the products.
  H2O ( energy is released)   • We use lime water and
                                collect the colourless liquid
                                produced in a U tube. (CO2 +
 The Carbon Cycle
• These 2 reactions working       • Photosynthesis and
  together make part of the         respiration are the chemical
  Carbon Cycle.                     opposites of one another.
• Humans can destroy the            When they work together
  balance by:                       without intervention they
   Burning – CO2 is produced.       ensure the correct balance of
                                    gases in the air.
• Chopping down trees/plants-
  less photosynthesis therefore   • We breathe out CO2. Plants
  too much CO2 and less O2 in       use this in Photosynthesis.
  the atmosphere.                   They give out O2. We require
                                    this for respiration.
• When any C compound is
  burned CO2 is produced          • Plants go through respiration
                                    when there is no sunlight.
  ( Fossil Fuels)
 Testing for Carbohydrates
• Iodine test               • Benedict’s Test
• Starch will turn Iodine     (Fehling’s)
  solution from brown to    • Monosaccharides and
  blue/black.                 disaccharides – except
                              sucrose will turn
                              Benedict's reagent from
                              blue to orange.
 Properties of Carbohydrates
• Mono and disaccharides       • Starch is not sweet
  are usually soluble in         tasting. It forms a colloid
  water. If you shine a          in water – it looks as if it
  beam of light through it,      has dissolved but if you
  the light will pass strait     shine a beam of light
  through.                       through it you can see
• They are sweet tasting.        the particles. The
                                 molecules are too big to
 Making long chain Carbohydrates
• Disaccharides and polysaccharides are made
  when monosaccharides undergo condensation
  polymerisation. 1 water molecule is released for
  every two monomers joined.
• Example
• Glucose +Glucose —> maltose + water
• C6H12O6 + C6H12O6 —> C12H22O11 + H2O
 Breaking Long Chain Carbohydrates
• Hydrolysis is the break down of Carbohydrates into
  smaller molecules. E.g. Starch being broken down into
  Glucose. This is the opposite of polymerisation. A
  water molecule has to be added back – hydrolysis.
• An acid or enzyme has to be present for this to happen.
• Sucrose breaks down to give 1 fructose molecule and 1
  glucose molecule.
• Sucrose —> glucose + fructose
  C12H22O11 Acid/enzyme C6H12O6 + C6H12O6
• When we eat starchy food our bodies break it down into
  smaller molecules so they can pass through the gut wall
  into the blood.
• This is another example of Hydrolysis.
• It starts off in the mouth. Saliva contains an enzyme,
  amylase, which starts to break down the starch.It
  continues in the stomach, where acid is found.
• (C6H10O5)n—>C6H12O6
          – Acid/enzyme
    Digestion in the lab
• Place starch solution in 3 different test-tubes
• To one add amylase
• To another add acid
• Add nothing to the third
• Place all 3 in water bath at 37C ( body T)
• Test each test-tube with Benedict’s solution after a few
• The test-tubes with the acid and amylase will turn
  orange – proving the starch has been broken down into
 Identifying the products of
• Look at how far each         • We can use
  spot has travelled.            CHROMATOGRAPHY
                               • Spot the paper with:the
• Compare the spots of the
                                 products of hydrolysis of
  mono and disaccharides         starch(H1) and sucrose(H2)
  with H1 and H2.                and mono and disaccharides.
• Match up the spots at        • Do not mix the spots.
  same level to identify the   • Let the chromatography run.
  which type of sugar is       • Look at results
  produced in Hydrolysis.
• Equation                      • This is the process of
• C6H12O6 →C2H5OH                 making Alcohol from
        +CO2                    • Small sugar molecules
                                  can be converted to
• C2H5OH is ethanol.              alcohol, using the
• It is part of the Alkanols.     enzyme Zymase, which
• This is another                 is found in yeast.
  homologous series.            • Carbon dioxide is also
 Alcoholic Drinks
• Alcohol slows down our     • You can make alcohol
  reactions.                   from any carbohydrate
• Too much can damage          source.
  our livers.                • Source Alcohol
• It can also be used as a   • Barley Beer/Whiskey
  fuel.                      • Apples     Cider
                             • Grapes Wine/Sherry
                             • Potatoes Vodka
• We place the impure alcohol      • WE can increase the
  in the distillation flask with
  antibumping granules.              strength of alcohol by
• Heat up the mixture.               distilling it. This removes
• Ethanol has BP of is 78C,          any impurities.( normal
  water is 100C.                     alcohol concentration in
• The alcohol will boil first,       fermentation is 15% -
  pass along delivery tube and       any stronger and the
  condense back to liquid.
                                     enzyme is destroyed –
• WE can repeat this process
  to purify it even more.            DENATURED)
• Spirits are distilled.
 Making Whisky
• Step 3 Fermentation              • Step 1 – Malting
• Yeast added – Glucose
  brakes down into ethanol and     • Barley is Hydrolysed into
  Carbon dioxide                     Maltose (uses enzyme in
• Step 4 – Distilling                Barley) – Green Malt
• To purify whisky – increase      • Step 2 – Mashing
• Step 5 – Blending                • Green Malt roasted on
• Mix different whisky’s then        peat fire and Mashed
  bottle them( malt whisky - not

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