Biology paper 1

• Enzymes


  Chemical substances produced by living things that act as catalysts to speed up chemical reactions
• Chemical reactions are what make you work. And enzymes are what make them work
• Enzymes


  • Are Catalysts
  • Produced by Living Things
• How enzymes work


  1. Living things have thousands of different chemical reactions going on inside them all the time

  2. These reactions need to be carefully controlled to get the right amounts of substances

  3. Raising the temperature can speed up reactions but also damages cells

  4. Living things produce enzymes that act as biological catalysts to speed up useful reactions without high temperatures
• Catalyst


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


  • Are all large proteins
  • Made up of chains of amino acids
  • Folded into unique shapes to do their jobs
• Enzyme active site


  • Has a unique shape that sits onto the substance involved in a reaction
  • Enzymes usually only catalyse one specific reaction
  • The substrate has to fit into the active site for the enzyme to work
• Lock and key model of enzyme action


  The substrate fits into the enzyme's active site like a key fits into a lock
• The active site changes shape a little as the substrate binds to it to get a tighter fit, called the "induced fit model of enzyme action
• Enzymes speed up chemical reactions
• The substance has to fit the enzyme's active site for the enzyme to catalyse the reaction
• Topic 2-Organisation


  • Most enzymes work best at a particular temperature and pH
  • Enzymes can be denatured by changes in temperature or pH