chapter 2 - enzymes

• endothermic

  • requires energy input
• exothermic

  • energy is given off
• enzymes are picky

  • catalyze single reaction or a class of reactions
• most enzymes have the prefix -ase
• enzyme substrate complex

  • active site is where substrate is held within an enzyme during a chemical reaction
• enzymes require nonprotein molecules called cofactors

  • enzymes without cofactors --> apoenzymes
  • enzymes with cofactors --> holoenzymes
• 2 types of cofactors

  • small metal ions
  • small organic groups - "coenzymes"
• enzyme kinetic is dependent on the conditions

  • temperature
  • pH
  • concentration of substrate and/or enzyme
• multiple binding sites

  • active site - where main reaction occurs
  • allosteric site - regulate enzyme activity

  these can both be either activators or inhibitors
• inhibition

  2 types

  • feedback
  • reversible
• feedback inhibition

  • way enzymes are controlled in biological systems
  • often seen in how hormones function in our body
  • when there's enough product formed, it binds to enzyme, stopping further production
• reversible inhibition

  • competitive inhibition - inhibitor blocks active site of enzyme, preventing binding
  • non-competitive inhibition - inhibitor binds to a different site on the enzyme, changing its shape
  • irreversible inhibition - inhibitor binds to enzymes in a way that permanently changes or blocks the site
• inactive enzymes

  • certain enzymes can be dangerous if activated prematurely
  • to prevent, these enzymes are initially produced in a dominant form called zymogens
  • zymogens block activity until they reach intended location