Biology - B2.3 - Enzymes

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B2.3.1 - Proteins, Catalysts and Enzymes

  • Protein molecules - long chains of amino acids folded to make specific shape - shape depends on function - can be: structural components of tissues, eg. muscle, hormones, antibodies, catalysts
  • Large proteins that control chemical reactions in cells called enzymes
  • Enzymes - biological catalysts - speed up reactions
  • Enzyme shape is vital for function - shape has an area where molecules can fit - active site
  • Substrate in a reaction held in active site can be connected to another molecule or broken down
  • Enzymes can:
    • build large molecules from smaller ones - build starch from glucose
    • change one molecule to another - one type of sugar to another
    • break down large molecules to smaller ones - all digestive enzymes
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B2.3.2 - Factors Affecting Enzyme Action

  • Enzyme reactions - similar to other reactions when temperature is increased
  • Reactions happen faster when warmer - higher temperature = molecules move around quicker = more collisions more often with more energy
  • Temperature too hot = enzyme stops working as active site changes shape - denatured
  • Each enzyme works best in different pH values - some in acidic, eg. stomach, others neutral or alkaline
  • pH too acidic/alkaline for enzyme = active site changes shape - denatured
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B2.3.3 - Enzymes In Digestion

  • Some enzymes work outside cells - digestive enzymes are produced by specialised cells in glands and the gut lining -> enzymes pass out of cells and come into contact with food
  • Digestion - involves breakdown of large insoluble molecules to smaller soluble molecules
  • Amylase - a carbohydrase - produced by salivary glands, pancreas and small intestine - catalyses digestion of starch to sugars in mouth and small intestine
  • Protease - proced by stomach, pancreas and small intestine - catalyses breakdown of proteins to amino acids in stomach and small intestine
  • Lipase - produced by pancreas and small intestine - catalyses breakdown of lipids (fats and oils) to fatty acids and glycerol
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B2.3.4 - Speeding Up Digestion

  • Protease - in stomach - works best in acidic conditions - glands in stomach wall produce hydrochloric acid to create very acidic conditions
  • Amylase and lipase - in small intestine - work best in slightly alkaline conditions
  • Liver produces bile - alkaline - stored in gall bladder - squirted into small intestine and neutralises stomach acid - makes small intestine conditions slightly alkaline
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B2.3.5 - Making Use of Enzymes

  • Some microorganisms produce enzymes that pass out of their cells - many uses in industry but can be costly to produce
  • Biological detergents - contain protease and lipase that digest food stains - work at lower temperatures - saves energy and money on electricity
  • Proteases - used to pre-digest some baby foods
  • Isomerase - used to convert glucose syrup to fructose syrup - more sweeter = less needed = not as fattening
  • Carbohydrase - used to convert starch to sugar syrup for food
  • Enzymes used in industry to bring about reactions at normal temperatures and pressures - traditional chemical processes require expensive equipment and lots of energy to produce high temperatures and pressures
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B2.3.6 - High-Tech Enzymes

  • Adv of using enzymes:
    • very effective at removing stains as washpowders
    • washpowders work at lower temperatures - saves energy and money
    • used in medicine to diagnose, control and even cure diseases
    • cost of equipment and energy reduced in industry
  • Disadv of using enzymes:
    • misusing washpowders can mean allergic reactions - enzymes inclosed in capsules and hands shouldn't be put under water if powder dissolves
    • enzymes may enter waterways via sewage system
    • industrial enzymes can be costly to produce
    • high temperatures - needed to kill pathogens but enzymes denature
    • protease will digest some fabrics, eg. wool
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