Temperature

• Graph A

  A) temperature

  B) optimum temperature

  C) 37 C

  D) temperature (C)

  
• Affect of Temperature

  • Rise to optimum (temperature with max ESC formation)
  • Increases enzyme and substrate kinetic energy
  • More frequent and energetically successful collisions
  • Form more ESCs
  • Increase rate
  • Above optimum
  • Enzymess vibrate more
  • Increased thermal energy input
  • Weaker bonds (hydrogen and ionic) break
  • Active site changes
  • Fewer ESCs
  • If enough break
  • Tertiary structure unravel
  • Irreversible shape change
  • Denaturation
  • Time-dependent: High temps for short time has less impact than prolonged exposure
  • Optimum for many mammalian enzymes is 40°C - 50°C
• Temperature Coefficient (Q_10)

  • Effect of 10°C temperature rise on enzyme’s rate
  • Q_10 = Rate (T+10)°C/rate at T°C
  • T = temperature
  • Enzyme rate doubles for each 10°C rise in temperature (Q_10 = 2) in most reactions between 40°C and optimum
  • Can’t be used at or after optimum temperature
  • More enzymes are denatured
  • Reduces rate