enzymes

• Enzymes


  Tertiary structure proteins that catalyse reactions by lowering activation energy

  • each enzyme only catalyses one specific reaction due to unique active site shape (complementary to one substrate) this is due to specific folding/bonding
• Lock and key model


  • Enzyme acts like a lock, substrate is a key
  • Active site is fixed shape
  • substrate collides and attaches to enzyme through random collisions
  • Charged groups within active site distort substrate, lowering the activation energy
  • Products released, the active site is empty and ready to be reused
• Induced fit model


  • Enzyme acts like a glove, substrate is your hand
  • Active site not complementary to substrate - moulds around substrate (changes shape) to perfectly fit
  • This puts strain on bonds (easier to break) which lower activation energy
  • Products removed, active site returns to original shape
• Competitive inhibitor


  • Sits in active site, blocks substrate from binding
  • Temporary - active site's tertiary structure unchanged
• Non-competitive inhibitor


  • Binds to enzyme in location other than active site
  • Permanently changes active site (tertiary structure)
  • No longer complementary to substrate