Factors affecting enzyme activity

• Factors that affect enzyme activity:

  • Temperature
  • pH
  • Substrate and enzyme concentration
• Increasing temperature:

  Kinetic energy of particles increased as they move faster and collide more often - Rate of reaction increased
• Temperature coefficient - Q10:

  Measure of how much that rate of reaction INCREASES with a 10 degrees Celsius rise in temperature
• Temperature coefficient:

  Rate of reaction doubles with a 10 degrees Celsius temperature increase
• Denaturation from temperature:

  1. Higher temperatures - Bonds vibrate more
  2. Vibrations increase until bonds are strained then break
  3. Specific 3d tertiary structure changes
  4. Enzyme denatured
• Denatured enzymes:

  1. Active site begins to change shape
  2. No longer complementary to substrate
  3. Substrate can no longer fit into active site and does not function as a catalyst
• Optimum temperature - Temperature enzymes have the highest rate of activity
• Most enzymes optimum is around 40 degrees Celsius
• Change in pH = Change in hydrogen ion concentration
• Specific 3d tertiary structure held in place by hydrogen and ionic bonds between R-groups
• Ionic and hydrogen bonds are from interactions between polar and charged r-groups on amino acids - Primary structure formed
• More hydrogen ions = Low pH (Acidic)
• Fewer hydrogen ions = High pH (Alkaline)
• Optimum pH - Active site at the right shape at a certain hydrogen ion concentration
• Renaturation - pH changing back after optimum is surpassed and its active site is altered then returning back to normal shape
• Denatured = When pH has a more significant change - Structure of the enzymes is irreversibly altered and active site is no longer complementary to substrate
• Enzyme denatured - Rate of reaction is reduced
• Changing concentration of hydrogen ions - Changes interactions hydrogen ions have with polar and charged R-groups
• Interactions of R-groups together - Affected by interaction of R-groups with hydrogen ions
• More hydrogen ions present (Low pH) or Less hydrogen ions present (High pH):

  1. Less the R-groups are able to interact with each other
  2. Bonds break
  3. Enzyme shape changes
• Shape of enzymes changes as pH changes - Only functions within a narrow range
• Increasing substrate concentration:

  1. Higher collision rate - More enzyme-substrate complexes formed
  2. Rate of reaction increases
• Increasing concentration of enzymes:

  1. Number of available active sites increased
  2. More enzyme-substrate complexes are formed at a faster rate
• Rate of reaction increases until Vmax
• At Vmax:

  1. All active sites are occupied by substrate particles
  2. No more enzyme-substrate complexes can be formed until products are released from active sites
• Increase rate of reaction past Vmax - Add more enzymes or increase temperature
• Adding more enzymes past Vmax:

  1. More active sites are available
  2. Rate of reaction rises towards a higher Vmax
  3. Concentration of substrate becomes the limiting factor again - If increased rate of reaction rises until the higher Vmax is reached