bio- how enzymes work

• Enzymes


  Catalysts made by living organisms
• Enzymes


  • They are large proteins made up of long chains of amino acids
  • They can fold into different shapes, each shape being a unique enzyme that catalyzes a particular chemical reaction
• How enzymes work


  1. Enzyme has an active site with a unique shape complementary to the substrate

  2. Substrate binds to active site

  3. Enzyme catalyzes the reaction

  4. Products are released
• Catalyst


  A substance that increases the speed of a chemical reaction without being changed or used up in the process
• Most chemical reactions are naturally quite slow

  Enzymes speed up the process
• Increasing temperature


  Can damage cells and speed up unwanted reactions and require lots of energy
• Lock and key model


  Original model where substrate has to fit perfectly into the active site of the enzyme
• Induced fit model


  More realistic model where the enzyme changes shape slightly to better fit the substrate
• The active site of an enzyme is complementary to the substrate
• The induced fit model is like putting your hand into a rubber glove - the glove molds around your hand to become a perfect fit
• How temperature and pH affect the functioning of enzymes and the rate of enzyme controlled reactions


  1. Temperature increases

  2. Rate of reaction increases

  3. Temperature reaches 37 degrees

  4. Rate of reaction starts to drop rapidly

  5. Enzyme becomes denatured at around 45 degrees

  6. Optimal temperature is 37 degrees
• Denatured


  Enzyme's shape changes so much that the substrate can no longer bind to the active site
• Optimal temperature


  The temperature at which the rate of reaction is highest
• How pH affects enzymes

  1. pH gets too high or too low

  2. Bonds holding the enzyme together start to break

  3. Active site changes shape

  4. Substrate can still fit but less well than normal, slowing down the rate of reaction

  5. Active site changes shape so much that the substrate can't fit at all, enzyme becomes denatured
• Optimal pH


  The pH at which the enzyme works best
• Most enzymes in our body work best at neutral pHs of around 7
• Enzymes that work in the stomach have an optimal pH of around 2 to function in the acidic environment