Enzyme

• Enzyme action 

  1. Enzymes lower the activation energy for a reaction. 
  2. The substrate molecule(s) have a high affinity for the active site 
  3. Induced fit occurs when the active site changes shape to better fit the substrate after the substrate binds.  
  4. Induced fit ensures that the active site comes in very close contact with the molecules of substrate increasing the chance of the chemical reaction taking place. 
  5. The product(s) have low affinity allowing them to leave the active site. 
• Enzyme inhibition

  
  

  6. Metabolic pathways can be controlled through competitive, non-competitive and feedback inhibition of enzymes.

  7. Competitive inhibitors bind at the active site preventing the substrate from binding.

  8. Competitive inhibition can be reversed by increasing substrate concentration.

  9. Non-competitive inhibitors bind away from the active site but change the shape of the active site preventing the substrate from binding.
• Enzyme inhibition

  
  

  10. Non-competitive inhibition cannot be reversed by increasing substrate concentration.

  11. Feedback inhibition occurs when the end-product in the metabolic pathway reaches a critical concentration.

  12. The end-product then inhibits an earlier enzyme, blocking the pathway, and so prevents further synthesis of the end-product.