Enzymes - AQA GCSE BIOLOGY

• "The enzyme is the biological catalyst"
• Enzymes are proteins that speed up chemical reactions without being used up or changed themselves.
• All living organisms need enzymes to carry out life processes, such as digestion, growth and repair.
• Enzymes have an active site where substrate molecules fit into.
• An enzyme has an active site where substrate molecules bind to it, forming an enzyme-substrate complex (ES). The enzyme then changes the shape of the substrate so that a reaction can take place more easily.
• Substrates fit into the active sites on enzymes like keys fitting locks.
• An enzyme has an active site which is where the substrate binds to it.
• Enzymes are proteins that speed up reactions without being used up or changed themselves.
• Once the product(s) have been formed they leave the ES complex and the enzyme returns to its original shape ready to react with another substrate molecule.
• An enzyme's shape determines its function.
• Enzymes lower activation energy by bringing reactants together and holding them close enough so they can collide with sufficient force to form products.
• Enzymes work best at specific temperatures called optimum temperature.
• Active sites are specific so only certain substrates can bind with them.
• When the substrate fits perfectly it forms an enzyme-substrate complex which then breaks down to form products.
• Each enzyme speeds up only one type of reaction.
• When a substrate fits perfectly into its active site, this is called complementary fit.
• If there is no perfect match between the substrate and the active site, the reaction rate will be low because not all the substrate molecules will react with the enzyme.
• The rate at which an enzyme works depends on temperature, pH and concentration of both the enzyme and substrate.
• If the temperature continues to increase above the optimum temperature, the rate decreases again due to denaturation.
• The lock and key model suggests that only one type of substrate will fit into the active site of an enzyme.