Activation energy & enzymes

• • Enzymes are globular proteins

  • They possess a small region called the active site where the reaction occurs
• • Activation energy is the amount of energy necessary to push the reactants over an energy barrier.

  – At the summit the molecules are at an unstable point, the transition state.
• Without enzymes, biochemical reactions would take place so

  slowly that life as we know it would cease to exist.
• • The energy required to break chemical bonds in the reacting chemicals is called the activation energy

  • Enzymes lower the activation energy
• Specificity - The molecules of substrate show affinity (chemical attraction) for the enzyme's active site.
• • Enzymes are substrate specific. The active site is a specific shape.

  • This means they only act on a single substrate.
• Induced fit - The substrate molecule induces a slight change in the shape of the active site to allow the substrate molecule to fit perfectly.

  The change in shape of the active site facilitates the reaction.
• Induced fit makes sure

  the active site comes into

  very close contact with

  substrate molecules.

  Increases the chance of

  the reaction taking place
• The energy required to break chemical bonds in the reacting

  chemicals is called the activation energy. Enzymes are proteins which lower the activation energy needed for a chemical reaction to take place.