2.1.2 Enzyme Action

• What forms when specific substrates bind to enzymes?

  Enzyme-substrate complex
• Why does the active site of an enzyme have a specific shape?

  To fit a specific substrate
• What can change the shape of an enzyme's active site?

  Extremes of heat or pH
• What is denaturation in enzymes?

  Change in shape preventing substrate binding
• What must happen for a reaction to occur at the active site?

  Substrates must collide correctly
• What determines the specificity of an enzyme?

  Complementary shape of active site
• How is the shape of an enzyme's active site determined?

  By the enzyme's tertiary structure
• What holds amino acids together in proteins?

  Peptide bonds
• What happens if the order of amino acids in a protein is altered?

  The three-dimensional shape changes
• What is an example of enzyme specificity?

  Catalase binds to hydrogen peroxide
• What is formed when an enzyme and its substrate join together?

  Enzyme-substrate complex
• How long does the enzyme-substrate complex last?

  It is formed temporarily
• What does the lock-and-key hypothesis describe?

  Enzymes and substrates fit precisely together
• Who proposed the lock-and-key hypothesis?

  Emil Fischer
• What does the induced-fit hypothesis suggest?

  Enzymes and substrates can change shape
• What are conformational changes in enzymes?

  Shape changes during substrate binding
• How do enzymes lower activation energy?

  By providing an alternative energy pathway
• What is activation energy?

  Energy needed for a reaction to occur
• What happens to bonds in reactants when enzymes are present?

  Bonds become less stable
• What would happen without enzymes in biological reactions?

  High temperatures or pressures would be needed
• What is the effect of enzymes on cell conditions?

  They avoid extreme conditions
• What are the key features of the lock-and-key and induced-fit hypotheses?

  • Lock-and-key hypothesis:
  • Enzymes and substrates fit precisely
  • Rigid structures

  
  

  • Induced-fit hypothesis:
  • Enzymes and substrates can change shape
  • Ensures optimal binding arrangement
• What are the steps in enzyme action from substrate binding to product release?

  1. Substrate binds to active site
  2. Enzyme-substrate complex forms
  3. Reaction occurs
  4. Products are released
• How do enzymes affect the activation energy of reactions?

  • Enzymes lower activation energy
  • Provide alternative energy pathways
  • Allow reactions to occur under mild conditions