Enzymes

• Enzymes


  Proteins that act as biological catalysts
• Catalyst


  A substance which speeds up the rate of reaction in chemical reactions, without being used up
• Enzymes are not changed by the reaction and can be used repeatedly
• Metabolic reactions


  Reactions that would take too long to occur without enzymes
• Enzyme action


  • Contains an active site which is a sequence of amino acids with a specific shape
  • The shape is complementary to the substrate
  • When the enzyme breaks the substrate down, the substrate enters the active site to form an enzyme-substrate complex
  • The substrate is broken down and the product is released
  • The enzyme can then bind to another substrate molecule
• Each enzyme is complementary to only one type of substrate
• Proteases


  • Break down proteins so that amino acids can be absorbed into the blood
• Carbohydrases


  • Break down carbohydrates
• Factors affecting enzyme action

  • pH - enzymes have an optimum pH that they work best at
  • Temperature - As the temperature increases up to the enzyme's optimum, the rate of reaction increases. At very high temperatures above the optimum, the enzymes become denatured and the active site changes shape
• Active site

  A specific region of an enzyme where the substrate binds and the reaction takes place
• As the pH moves away from the optimum

  The rate of reaction decreases
• The change in pH

  Causes the shape of the active site to change
• Catalyst


  A substance that increases the rate of a chemical reaction without being changed itself
• The shape of the active site changing


  Means the substrate cannot fit in the active site, hence no enzyme-substrate complexes can form
• Denaturation


  Exposure to high temperatures or extremes of pH, produces a permanent change in the shape of an enzyme's active site that prevents the binding of a substrate
• Denatured


  The enzyme has become unusable
• Enzyme


  A biological catalyst that increases the rate of reactions in living organisms
• As the temperature increases up to the enzyme's optimum


  The rate of reaction increases
• Enzyme-substrate complex


  The temporary complex formed when the substrate binds to the active site of the enzyme
• The molecules have more kinetic energy


  They move faster
• More successful collisions


  More enzyme-substrate complexes can form
• Rate of reaction


  The speed at which reactants are converted into products
• At very high temperatures above the optimum


  The enzymes become denatured and the active site changes shape
• Substrate specificity


  The ability of an enzyme to catalyse only a specific reaction or set of reactions which have substrates complementary to the shape of the enzyme
• The active site changing shape

  Decreases the rate of reaction as enzyme-substrate complexes cannot form
• Substrate specificity


  The ability of an enzyme to catalyse only a specific reaction or set of reactions which have substrates complementary to the active site of the enzyme