Lock and Key Model

• The model than an enzyme acts upon is called its substrate
• Enzyme reactions can be summarised by the equation: substrate+enzyme ---> products
• enzyme molecules are folded into a special shape
• Letter: A

  
• Letter: C

  
• Letter: D

  
• Letter: A

  
• Compared to the start of the reaction, the enzyme molecule at the end is exactly the same
• the part of the enzyme molecule where the substrate fits in is called the active site
• this picture of how enzymes work is sometimes called the enzyme substrate complex

  
• for it's function, the shape of an enzyme molecule is essential
• if an enzyme molecule is heated too much, it denatures-its shape is changed or destroyed
• How enzymes behave at different temperatures is best summarised by: different enzymes work best at different temperatures
• if an enzyme molecule is heated too high a temperature, it permanently stops working
• how an enzyme behaves at different level of acidity is best summarised by: each enzyme has a PH that it catalyses fastest