Enzyme Action

• What are enzymes and what do they do?

  Enzymes are globular proteins and biological catalysts responsible for speeding up the rate of chemical reactions within cells
• Can enzymes be reused?

  yes, they remain unchanged so can be used again
• How do enzymes act as biological catalysts?

  they lower the activation energy of a reaction by finding an alternative pathway that requires less energy
• What is the activation energy?

  the minimum amount of energy that needs to be supplied to the chemicals before the reaction can start
• How can you form an enzyme-substrate complex?

  a substrate with a complementary shape binds to the active site of an enzyme to form an enzyme-substrate complex
• What does the specific tertiary structure of an enzyme form?

  a specific active site
• What is the active site?

  the part of an enzyme where the substrate molecules bind to
• What is a substrate?

  a molecule which the enzyme acts on, fits neatly into the active site
• How are substrate molecules held within the active site?

  they are held by bonds that temporarily form between amino acids of the active site and they group on the substrate
• Give 2 way an enzyme-substrate complex can lower the activation energy?

  1. holding the 2 molecules to be joined close to each other, reducing any repulsion so they will bond more easily
  2. creating a strain on the bonds of a substrate as it fits into the active site allowing them to break more easily
• What happens if the tertiary structure of an enzyme becomes altered?

  the shape of the active site would change, this causes the complementary substrate to no longer fit and an E-S complex won't be formed
• What things can alter the tertiary structure?

  1. changes in pH or temperature
  2. changes in amino acid sequence by mutations in the gene that encodes the enzyme
• How can lowering the activation energy increase the rate of reaction?

  lowering the AE reduces the temperature needed for the reaction to take place which increase the ROR
• What is the induced fit model?

  as the substrate binds to the complementary active site, the active site changes shape and moulds itself around the substrate to accommodate its shape
• What is the lock and key model?

  the shape of a substrate (key) exactly fits into the active site of a particular enzyme which is considered to be rigid like a lock
• What happens to the substrate as the enzyme begins to change shape?

  the enzyme puts strain on the substrate, this distorts the particular bonds in the substrate hence lowers the activation energy needed to break the bond