Practical 5: determination of activation energy of an enzymed catalyzed reaction
enzymes are complex chemicals that control reactions in living cells. They are biochemical catalysts, speeding up reactions that would occur too slowly to be of any usefulness to an organism. Although in organisms, it is not necessary for the reactions to be at maximum rate at all times. Enzymes interact with other molecules to produce a stable system in which the products are made when they are needed in the exact amount. An enzyme lowers the activation energy of a reaction so its easier to proceed. Enzymes are specific to which substrates it binds with to the active site.(AS biology, 2008). There is a lock and key hypothesis, as shown in diagram 1: (http://www.skinnersbiology.co.uk/enzyme.htm)
the aim of this practical is to determine the activation energy of hydrolysis of p-nitrophenyl phosphate in the presence of the enzyme alkaline phosphate. In the first part of the experiment a procedure was carried out to prepare the calibration curve, which afterwards the concentration in nmol/ml was worked out. Experiment 2 was carried out to compare reaction rates at 2 set temperatures, allowing to source the effect of different temperatures on rates of reactions. Afterwards the activation energy is found using the Arrhenius equation.
as in practical guide
Experiment 1 calibration curve-
Table showing the absorbance and concentration of the 10 dilutions of p-nitrophenol at 405nm Tube no | blank | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 150 µM p-nitrophenol (ml) | 0 | 0.1 | 0.2 | 0.3 | 0.4 | 0.5 | 0.6 | 0.7 | 0.8 | 0.9 | 1.0 | Bicarbonate buffer (ml) | 1.0 | 0.9 | 0.8 | 0.7 | 0.6 | 0.5 | 0.4 | 0.3 | 0.2 | 0.1 | 0 | NaOH (ml) | 2.0 | 2.0 |...
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