B2 Unit 3 - Enzymes

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Protein, Catalysts and Enzymes

  • Protein molecules are made of long chains of amino acids
  • These chains fold to make specific shape and each shape gives it a different function
  • Four things proteins can be are:
    • Structural components of tissues, such as muscle
    • Hormones
    • Antibodies
    • Catalysts (Enzymes)
  • Enzymes control chemical reactions
  • They speed up reactions so are biological catalysts
  • The shape of the enzyme is very important as it determines which molecules can fit into it.
  • The place where the molecules attach is called the active site
  • A substrate is the molecule the enzyme acts on
  • An enzyme can either make the substrate attach to another molecule or break the substrate down
  • An example of an enzyme making a large molecule out of many small ones is:
    • making starch out of glucose
  • An example of an enzyme breaking down a molecule into smaller ones is:
    • Lipase breaking down fats into fatty acids and glycerol in the digestive system
  • An Enzyme can also change one type of molecule into another - eg. turning one type of sugar into another
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Factors Affecting Enzyme Action

  • Reactions with enzymes happen faster when the environment is wamer
  • However, if it gets too hot the enzyme denatures meaning the enzyme can no longer work. This is because the enzyme has lost it's shape.
  • An enzyme works best between the temperatures of 37 and 40 degrees centigrade. This is its optimum temperature.
  • The PH of the environment also affects the efficiency of the enzyme. Different enzymes work best in a different PH.
  • If the environment is too alkaline or acidic then the enzyme could denature.
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Enzymes in Digestion - Speeding Up Digestion

  • Digestive enzymes are produced from specialised cells in glands inside the gut
  • Digestive enzymes help wiht the process of breaking down large insoluble molecules into smaller soluble ones
  • There are three types of digestive enzymes, these are:
    • Amylase - breaks down strach into sugars such as glucose - is produced in the pancreas, mouth and small intestine
      • It works best in slightly alkaline conditions
    • Protease - breaks down proteins into amino acids - is produced in the pancreas, stomach and small intestine. There are two types: pepsim and tripsim and are found in different places.
      • It works best in acid conditions - therefore it works well in the stomach because glands in the wall of the stomach produce hydrochloric acid
    • Lipase - breaks down fats (lipids) into glycerol and fatty acids - produced in pancreas and small intestine.
      • It works best in slightly alkaline conditions
  • The liver produces bile in the gall bladder.
  • It is squirted into the small intstine
  • It neutralises the stomach acid
  • It makes them slightly alkaline
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Making Use of Enzymes

Some microorganisms pass enzymes out of their cells

These can be used in industry. Examples are:

  • Biological detergents - contain proteases and lipase that digest food stains. They work at lower temperatures than ordinary washing powders which reduces energy use and cost.
  • Proteases - used to pre-digest proteins in some baby food so that babies can still get the nutrients they need.
  • Isomerase - converts glucose syrups into fructose syrup. The fructose is much sweeter so less is needed to sweeten a food, making it less fattening.
  • Carbohydrases - convert starch into sugar syrup to sweeten food

Disadvantages of using enzymes include:

  • If they are misused theycan cause allergic reaction on the skin
  • They can cost a lot to produce
  • They denature at the high temperatures needed to kill the pathogens in the clothing
  • Some fabrics - like wool - can be digested by the proteases
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