Mass action rate laws:

Mass action kinetics state that the rate of a reaction is the product of a rate constant (k) times (x) the mass(S). The mass in our case is concentration of the substrate (S) of the reaction. kxS, commonly written kS

Mass action kinetics can be used to model (approximate) the behavior of reversible and irreversible enzymatic reactions for unregulated enzymes that are not near saturation.

Modeling reversible and irreversible reactions with mass action kinetics.

• irreversible reactions (uni-directional)

  Irreversible reactions are reactions that occur in only one direction. This includes uni-directional movement across a membrane through a channel and enzyme catalyzed reactions. For reactions with a single substrate, the rate law for the reaction is written k*S or simply kS.

  Mass Action Exercises

  Write the rate law for the following reactions based on mass action.

  Remember, the law of mass action states that the speed (rate) of the reaction is proportional to the concentration of the reactants/ substratea. This proportionality is most often a product of a rate constant (k) times (*) the concentration of the substrate (S).

  1.) A ->B

  2.) A+B->AB

  3.) A+B->C

  4.) C->A+B

  5.) A+B+C->ABC

  Solutions