Enzymes

• Enzymes


  Catalysts produced by living things that make chemical reactions work
• Enzymes


  • Living things have thousands of different chemical reactions going on inside them all the time
  • Enzymes reduce the need for high temperatures and only speed up the useful chemical reactions in the body
• Catalyst


  A substance which increases the speed of a reaction, without being changed or used up in the reaction
• Enzymes


  • They are all large proteins made up of chains of amino acids folded into unique shapes
  • Enzymes need their unique shape to do their jobs
• Substrate


  The substance that an enzyme acts on
• Enzymes


  • They usually only catalyse one specific reaction
  • This is because the substrate has to fit into the enzyme's active site
• Induced fit model


  The active site changes shape a little as the substrate binds to it to get a tighter fit
• As temperature increases


  The rate of an enzyme-catalysed reaction increases at first
• If temperature gets too high

  Bonds holding the enzyme together break, changing the shape of the active site, so the substrate won't fit anymore (enzyme is denatured)
• Enzymes


  • They have an optimum temperature where they work best
  • They also have an optimum pH that they work best at
• Pepsin is an enzyme used to break down proteins in the stomach, it works best at pH 2 which is well-suited to the acidic conditions there
• Digestive enzymes


  Break down big molecules like carbohydrates and fats into smaller molecules that can pass through the walls of the digestive system
• Carbohydrases


  Convert carbohydrates into simple sugars
• Carbohydrase


  • Amylase
• Amylase


  Breaks down starch, a carbohydrate, into maltose
• Places amylase is made


  • Salivary glands
  • Pancreas
  • Small intestine
• Proteases


  Convert proteins into amino acids
• Places proteases are made

  • Stomach (pepsin)
  • Pancreas
  • Small intestine
• Lipases


  Convert lipids into glycerol and fatty acids
• Places lipases are made

  • Pancreas
  • Small intestine
• Bile


  Neutralises stomach acid and emulsifies fats
• Places bile is produced and stored

  • Liver
  • Gallbladder
• The body makes good use of the products of digestion to make new carbohydrates, proteins and lipids. Some glucose is used in respiration.
• Bile is alkaline and neutralises the acidic conditions in the stomach, allowing enzymes in the small intestine to work properly.
• Bile emulsifies fats, breaking them into smaller droplets to increase the surface area for lipase enzymes to work on.