Rate Concentration Graph for Enzyme Catalysed Reaction
Let's take a look at the rate concentration graph of a reaction catalysed by enzymes.
Notice the rate increases initially then becomes constant as reactant concentration increases.
We can treat this as a combination of 2 separate graphs.
The point of intersection of these 2 graphs will coincide at the concentration of enzyme.
1. Reactant concentration less than enzyme concentration
When reactant concentration increases, there are enough enzymes to catalyse the additional reactants.
This leads to a proportionate increase in the rate of reaction.
The reaction is first order with respect to reactant and rate equation is as follows:
rate = k [reactant]
2. Reactant concentration more than enzyme concentration
At this stage saturation is reached and all the enzymes are fully utilised.
When reactant concentration increases, there is no additional enzymes to handle the catalysis.
Hence rate reaches a maximum and does not increase any further.
The reaction is zero order with respect to reactant and rate equation is:
rate = k
Therefore the rate concentration graph of an enzyme catalysed reaction is summarised here:
[reactant] less than [enzyme], first order wrt reactant, rate = k[reactant]
[reactant] more than [enzyme], zero order wrt reactant, rate = k
Topic: Kinetics, Physical Chemistry, A Level Chemistry, Singapore
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