Chap 5

• An enzyme-substrate complex is formed temporarily when the enzyme combines with the substrate
• Enzymes are crucial to living organisms as they speed up metabolic reactions necessary to sustain life
• Lock and key mechanism

  Enzyme and substrate molecules have complementary shapes like two pieces of a jigsaw puzzle
• Factors affecting enzyme activity

  • Temperature
  • pH
• Enzymes can be used over and over again because they are not used up during the reaction
• Catalyst


  Substance that increases the rate of a chemical reaction and is not changed by the reaction itself
• The enzyme itself is unchanged at the end of the reaction
• Enzymes work by binding with the substrate to form an enzyme-substrate complex, then the reaction occurs, and the enzyme product complex is formed
• Enzyme

  Proteins that speed up the rate of all metabolic reactions in living organisms
• Enzymes are specific to their substrate molecules due to complementary shapes of the active site and substrate molecule
• Active site

  Shape on the enzyme that exactly fits the substances on which it acts
• The rate of an enzyme-catalyzed reaction increases as the temperature increases
• Without digestive enzymes, animals would not be able to break down food molecules quickly enough to provide the energy and nutrients they need to survive
• Enzyme


  Biological catalyst made in living cells that speeds up the rate of metabolic reactions
• Substrate

  Substance on which the enzyme acts
• All enzymes have an optimum temperature where they work best, and if the temperature gets too high, the enzyme gets denatured
• Denaturation of enzymes occurs when the bonds in the enzymes break, causing the shape of the enzyme's active site to change
• Products


  Molecules produced after the reaction
• Effect of pH on enzymes

  pH affects enzyme activity, with enzymes having an optimum pH in which they work best. Deviation from the optimum pH can cause denaturation of enzymes
• Effect of pH on enzymes

  • Graph showing how pH affects the rate of a reaction with enzymes
• Most enzymes have an Optimum temperature of approximately 37 degrees Celsius in the human body and start getting denatured at above 50 degrees Celsius
• Enzymes will not function properly if the pH deviates too much from their Optimum, causing denaturation
• Examples of enzymes with different Optimum pH

  • Pepsin (Optimum pH of approximately two)
  • Amylase (Optimum pH of 7)
• Chapter 5 on enzymes covers the effects of temperature and pH on enzyme activity
• Pepsin works best in the stomach's acidic conditions at a pH of approximately two, while amylase, found in saliva, has an optimum pH of 7
• Effect of temperature on enzymes

  • Enzyme denaturation at high temperatures
• Effect of temperature on enzymes

  • Graph explaining how temperature affects enzyme activity
• Enzymes have an optimum pH in which they work best, and different enzymes may have a different optimum pH
• Effect of temperature on enzymes

  Temperature affects enzyme activity, with different enzymes working best at different temperatures. If the temperature gets too high, the enzyme will get denatured, causing the shape of the enzyme's active site to change. A change in the active site will cause the enzyme to stop working
• Enzymes speed up the reaction rate at their optimum pH but will not work efficiently outside that range