Enzymes and Metabolism

• Enzymes are proteins that allow chemical reactions to take place at normal body temperatures by increasing the rate of reaction
• Enzymes are substances that act as a catalyst in a chemical reaction
• Catalysts:

  • Increase rate of reaction
  • Make it easier to react
  • Do not change or get used up in the reaction
• Activation energy is energy that is needed to start the chemical reaction
• Enzymes are able to reduce the amount of activation energy needed
• Activation energy with and without an enzyme

  
• Enzymes act on substances
• Enzymes are each specific for only one substrate
• The enzymes and substrate in the lock and key model have a shape and structure that allows only them to fit together
• The active site is the part of the enzyme that combines with the substrate
• When locked together they are called the enzyme-substrate complex
• Lock and key model:

  A) substrate

  B) enzyme

  C) enzyme-substrate complex

  D) enzyme

  E) product

  
• Anabolic Enzyme Action

  • Help to build compounds in chemical reactions
  • Requires energy
  • Example is protein synthesis
• Catabolic Enzyme Action

  • Help to break down compounds in chemical reactions
  • Releases energy
  • Example is cellular respiration
• Five factors that affect the action of enzymes:

  • Concentration of enzymes and substrate
  • Temperature
  • pH
  • Cofactors and coenzymes
  • Inhibitors
• Enzyme concentration affect the action of enzymes as the higher the concentration, the faster the rate of reaction
• Substrate concentration affects the action of enzymes as increasing substrate concentration increases the rate of reaction
• Enzyme and substrate concentrations:

  
• Temperature affects the rate of most chemical reactions when heat is increased
• Most enzymes work in a limited range of 30-45 degrees, 30 degrees being the optimum temperature
• Since enzymes are proteins, the structure of the enzyme changes beyond 45-50 degrees and the enzyme becomes denatured and inactive
• Temperature:

  
• Enzymes are sensitive to pH
• Altering the pH of an enzyme can change the shape of the active site on the enzyme and will alter its fit with the substrate
• All enzymes have an optimum pH which they work best at
• pH:

  
• Co-factors and co-enzymes are non-protein molecules that help enzymes to work
• Inhibitors are substances that slow or stop enzyme's activity
• Inhibitors are used to control reactions so that products are produced in specific amounts
• Many drugs act as inhibitors such as penicillin