Enzymes

• What are enzymes?

  Globular proteins that act as biological catalysts and are soluble in water.
• Why are enzymes soluble in water?

  They have hydrophilic R groups on the outsidethat allow them to interact with water
• What do enzymes do?

  They speed up chemical reactions
• How do enzymes work (lock and key theory)?


  Either one molecule with a complementary shape or more than one molecule can fit into the active site.

  • Substrate molecules bind to the active site by forming temporary bonds with amino acids in the active site.
• How many reactions can each enzyme catalyse?

  One specific reaction due to only one shape of substrate fitting in the active site.
• How do enzymes reduce the activation energy required for a reaction?

  The charged side groups interact and assist in breaking/ forming bonds
• How do enzymes work (induced fit theory)?

  When a substrate enters the active site, the enzyme changes shape slightly to fit around the substrate.

  • only a specifically shaped substrate will induce the correct change in the shape of the enzyme's active site.
  • the slight shape change of the active site enables the substrate to react.
• How does changing enzyme concentration affect the rate of reaction?

  1. Enzymes reduce the amount of activation energy required for a reaction to start
  2. With a higher concentration, there are more collisions between enzymes and substrates
  3. Therefore more active sites are occupied, increasing rate of reaction
  4. However, this levels off when substrates become a limiting factor
• Why does increasing the temperature lead to a faster rate of reaction (enzymes)?

  Increasing the temperature increases the kinetic energy available.

  • this increases the frequency of enzyme substrate collisions
  • there are more enzyme-substrate complexes formed
  • use the Q10 value to show that activity changes with the temperature rise