Enzymes

• What are enzymes classified as?

  Biological catalysts
• What type of proteins are enzymes?

  Globular proteins with complex structures
• Why are enzymes called biological catalysts?

  They increase reaction rates without being used
• What do enzymes do to activation energy?

  They lower the activation energy required
• What is activation energy?

  Energy needed to start a reaction
• How do enzymes affect the temperature of reactions?

  They allow reactions at lower temperatures
• What are the two categories of enzymes?

  • Intracellular enzymes: act within cells
  • Extracellular enzymes: act outside cells
• What determines the shape of an enzyme's active site?

  Its unique tertiary structure
• What forms when a substrate binds to an enzyme's active site?

  An enzyme-substrate complex
• What happens to the enzyme after the reaction?

  It is free to be used again
• What are the two models of enzyme action?

  1. Lock and Key model
  2. Induced fit model
• How does the lock and key model describe enzyme action?

  The substrate fits perfectly into the active site
• What occurs in the induced fit model?

  The active site changes shape to fit the substrate
• What can cause enzyme denaturation?

  Change in temperature or pH
• What happens to the enzyme's active site during denaturation?

  It changes shape and no longer fits the substrate
• What factors affect enzyme action?

  1. Temperature
  2. pH
  3. Substrate concentration
  4. Enzyme concentration
• What is the effect of temperature on enzyme activity?

  Increases until optimum, then decreases
• What is the optimum temperature for enzymes?

  The temperature at which they work fastest
• What happens to enzyme activity at temperatures above optimum?

  Rate of reaction decreases until it stops
• What happens to enzymes in acidic conditions?

  H+ ions denature the enzymes
• How does pH affect enzyme activity?

  Each enzyme has an optimum pH
• What happens to enzymes in alkaline conditions?

  OH- ions denature the enzymes
• What is the effect of substrate concentration on enzyme activity?

  Increases until saturation point is reached
• What is the saturation point in enzyme activity?

  When all active sites are occupied
• How does enzyme concentration affect reaction rate?

  Increases until all substrates are acted upon
• What are the types of enzyme inhibitors?

  1. Reversible inhibitors
  2. Irreversible inhibitors
• What is the difference between reversible and irreversible inhibitors?

  Reversible form weak bonds; irreversible form strong bonds
• What are the two categories of inhibitors?

  1. Competitive inhibitors
  2. Non-competitive inhibitors
• How do competitive inhibitors affect enzyme activity?

  They bind to the active site, blocking substrates
• How can the effect of competitive inhibitors be reduced?

  By increasing substrate concentration
• How do non-competitive inhibitors affect enzyme activity?

  They bind away from the active site, changing shape
• What is the effect of increasing substrate concentration on non-competitive inhibitors?

  It has no effect on the rate of reaction
• What is the overall effect of enzyme inhibitors?

  • Decrease the rate of enzyme-catalysed reactions
  • Can be reversible or irreversible