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Overview
  • Kinetic theory 
    • for two molecules to react
      • they must be within bond-forming distance
      • possess enough kinetic energy to overcome the activation energy (Ea)
    • factors that affect these two conditions will either decrease or increase the reaction rate
      • temperature: causes an increase in kinetic energy
      • concentration of reactants: increases probability of collisions
  • Gibbs free energy change G) 
    • is the free energy change between the products and the reactants
    • reflects the direction of a reaction and amount of reactants and products at equilibrium, but does NOT determine the rates of reaction
      • ΔG < 0: reaction is spontaneous and favors product formation
      • ΔG = 0: reaction is at equilibrium and proceeds in both direction at equal rates
      • ΔG > 0: reaction is nonspontaneous and favors reactant formation
    • Ea determines the rate of the reaction
      • a large Ea will have a slower rate
      • a small Ea will have a faster rate
    • enzymes lower the Ea allowing the reaction to proceed at a faster rate 
      • enzymes do NOT change the ΔG of the reaction just the Ea
      • enzymes are sensitive to temperature and pH
Enzymes Kinetics
  • Michaelis-Menten Equation 
  •   
    • an equation that relates the initial reaction velocity (Vi) to the substrate concentration
      • Vmax is directly proportional to the [E] 
      • Km is the Michaelis-Menten constant which represents the substrate concentration at which Vi is half the maximum velocity (Vmax)
        • Km = [S] at 1/2 Vmax
        • Km is related to the enzyme's affinity for the substrate [S]
          • ↑ Km = ↓ affinity
          • ↓ Km = ↑ affinity
  • Lineweaver-Burk Equation
    • an inverted form of the Michaelis-Menten equation
      • used to calculate Vmax and Km from experimental data at below enzyme saturation levels
      • the equation is in the format y = ax + b (a is the slope and b is the y intercept)
        • y = 1/Vi
        • x = 1/[S]
        • a = Km/Vmax
        • b = 1/Vmax
      • helpful hints
        • the smaller value of -1/Km, the greater the Km
        • ↑ y-intercept = ↓ Vmax
 

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