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  • Created by: Sophie
  • Created on: 03-04-13 17:30

Digestive Enzymes

  • starch, protein & fats too big to pass through digestive system
  • sugars, amino acids, fatty acids & glycerol small enough, pass through easily


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  • produced in liver
  • stored in gall bladder
  • released into small intestines
  • an alkaline
  • hydrochloric acid in stomach makes ph too acidic for enzymes so it neutralises the acid
  • makes conditions alkaline, best for enzymes
  • emulsifies fats- breaks fat into tiny droplets
  • this gives a bigger surface area of fat
  • easier for lipase to work so faster digestion
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  • chemical reactions in the body are carefully controlled by enzymes
  • acts as biolgical catalysts (a catalyst is a subtance whioch increases the speed of a reaction without being changes or used up in the reaction)
  • reduces the need for high temps
  • only have enzymes to speed up useful reactions
  • proteins-made of chains of amino acids
  • act as structural compnents of tissue, horomones and antibodies
  • unique shape, fits onto substance involved in a specific reaction
  • only catalyse one reaction
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Tempreature, ph and Enzymes

  • Enzymes in human body work best at 37oc
  • too hot- bonds holding enzyes together break- destroys special shape-won't work-denatured
  • enzymes have optimum ph, often ph7 neutral
  • too high of too low ph- denatures enzyme
  • pepsin- breakes down protiens in stomach-works best at ph2- suitted to acid conditions

Graph showing pH and enzyme activity. Between pH 4.5 and pH 8, enzyme activity increases steadily. It peaks at pH 8, then decreases fairly rapidly (http://www.bbc.co.uk/schools/gcsebitesize/science/images/gcsechem_18part2.gif)Graph showing temperature and enzyme activity. Between 0 and 40ºC, enzyme activity increases steadily. It peaks at 40°C (optimum temperature), then decreases rapidly (http://www.bbc.co.uk/schools/gcsebitesize/science/images/gcsechem_18part1.gif)

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Uses of Enzymes

  • Sugar syrup:
    • used from making sweets and sports drinks
    • cheap strach solution made from water, potatoes and maize 
    • carbohydrase enzyme breaks down strach into sugar
  • Baby food:
    • babies digestive system not fully developed 
    • protease enyme added to break down protiens inot amino acids
    • easier for babies to absord nutreins 
  • Slimming foods:
    • fructose made from glucose using isomerase enzymes 
    • fructose is sweeter than glucose or surcose so you need less to get the same sweetness, less calories 
  • Biolgical detergents:
    • protease and lipase enzymes break down plant and animal matter 
    • ideal for removing stains 
    • more effective at lower temps than other types of detergents 
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Advantages and Disadvantages for Enzymes

  • Advantages 
    • Biodegradable 
    • Work in mild conditions reducing the need for dangerous chemicals- better for environment, saves energy
    • Specific, only catalyse reaction you want 
    • Can work for long time, after initial cost can be continually used for are cheap 
  • Disadvantages 
    • Rapidly lose their catalytic ability if subject to unfavourable conditions
    • Some can only be used once because they are denatured in process 
    • Expensive to produce 
    • Some people allergic to enzymes 
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