Determination of the Activation Energy of an Enzyme Catalysed Reaction

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Determination of the activation energy of an enzyme catalysed reaction

In this practical the aim for this experiment was to find out the catalytic power of alkaline phosphate, as well as the rate of reaction and the activation energy of p-nitrophenol phosphate. Enzymes are biological molecules that catalyse a chemical reaction. ‘Enzymes work by lowering the activation energy of a chemical reaction making it easier to proceed’ [1]. This allows molecules to have more energy therefore it makes them collide so that product can be formed much quicker. In order for enzymes to work properly the activation energy must be exceeded first. Enzymes are described as the lock and key complex. They have an active site which is specific to a binding site on a substrate molecule. When this happens the substrate changes shape therefore the product is formed. ‘The enzyme-catalyzed reaction is as follows: E + S=ES=EP=E + P where E is enzyme, S is substrate and P is product.’[2] Factors that affect enzyme activity are:

1. Temperature- at low temperatures the rate of reaction is low this is due to the fact that there is less collisions of the molecules therefore not possessing the activation energy needed for reaction to occur. 2. PH- high PH denatures proteins by disrupting the precise 3 dimensional arrangement of the Protein chain whereas low PH can affect the ionisation of the substrate. 3. Concentration of reactant and concentration of product- When the concentration of enzyme increased, the rate of reaction proportionally increases aswell. When the concentration of substrate is increased so does the rate of reaction until no further reaction takes place between the substrate and enzyme. 4. Presence of inhibitory chemicals

This practical introduces the activation energy of hydrolysis of p-nitro phenyl phosphate will be determined in the presence of the enzyme alkaline phosphatase. [3] Methods
As stated in practical guide.
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