enzymes and substrates
overall reaction: S -> P
step 1: E + S -> ES fast
step 2: ES -> E + S fast
step 3: ES -> E + P slow
what is the order of the reaction in E and what is the order of reaction in S?
To determine the order of reaction with respect to E (enzymes) and S (substrates), we need to look at the rate equation. The rate equation describes the relationship between the rate of the reaction and the concentration of the reactants.
In this case, we have three steps in the reaction mechanism. The first step (E + S -> ES) and second step (ES -> E + S) are fast, which means they occur rapidly and do not significantly affect the overall rate of the reaction. The third step (ES -> E + P) is slow, meaning it is the rate-limiting step and determines the overall rate of the reaction.
The rate equation for this reaction can be written as follows: Rate = k[ES], where k is the rate constant and [ES] represents the concentration of the ES complex.
Now, let's analyze each reactant separately:
1. Order of reaction with respect to E (enzymes):
As we can see from the rate equation, the rate of the reaction is directly proportional to the concentration of ES complex ([ES]). Since ES is formed in the first step and consumed in the third step, the concentration of ES will change throughout the reaction. Therefore, the order of reaction with respect to E is 1st order.
2. Order of reaction with respect to S (substrates):
Looking at the reaction mechanism, we can see that S is involved in the first step (E + S -> ES) but does not appear in the rate equation. This indicates that S does not affect the rate of the reaction. Therefore, the order of reaction with respect to S is zero order.
In summary, the order of reaction with respect to E is 1st order, and the order of reaction with respect to S is zero order.