5 - Enzymes

• Enzyme

  A biological catalyst that speeds up chemical reactions in living organisms
• Catalyst


  Substance that increases the rate of a chemical reaction and is not changed by the reaction
• Enzymes

  Proteins that act as biological catalysts, instructed by DNA
• Enzymes are important to ensure the rate of reactions are fast enough to sustain life
• Processes sped up by enzymes

  • Digestion
  • Seed germination
  • Breakdown of toxins in liver and potato cells
  • Building of starch from glucose
• Enzymes in digestion

  • Amylase
  • Protease
  • Lipase
• Enzymes named according to the reaction they catalyze

  • Carbohydrase
  • Protease
  • Lipase
• Substrate


  Substance to be changed
• Product


  The substances made by the reaction
• Active site

  Place where substrate binds to the enzyme
• Lock and Key Mechanism

  1. Substrate fits into active site

  2. Enzyme-substrate complex forms

  3. Enzyme breaks down substrate

  4. Products are formed
• Enzymes

  • All enzymes are proteins
  • Enzymes are specific due to their complementary shape
  • Enzymes can be used over and over again
• Enzymes denature at low/high temperatures and extreme pH levels
• Effect of temperature on enzyme activity

  1. Lower temperature reduces kinetic energy

  2. Higher temperature increases kinetic energy

  3. Optimum temperature is 37°C

  4. Above 37°C, enzymes denature
• Effect of pH on enzyme activity

  1. Higher than optimum pH causes denaturation

  2. Lower than optimum pH reduces collisions

  3. Optimum pH is specific for each enzyme
• At optimum temperature, enzyme activity reaches its peak
• Enzymes lose their shape when denatured
• Less enzyme-substrate complex forms when enzymes are denatured
• Higher frequency of effective collisions increases the rate of reaction
• Enzymes are specific because only substrates with complementary shape can fit into the active site