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Introduction

Summary Aim A series of experiments involving the enzyme Catalase has been performed in order to determine some of the enzyme's properties. The enzyme had its reaction rate found in different conditions. Variation of enzyme concentration, variation of pH, variation of temperature, and the effect of different concentrations of inhibitors were all tested. Increasing the enzyme concentration increased the reaction rate. An optimum pH and temperature were found for the enzyme, outside of this optimum the reaction rate would be lower. As inhibitor concentration rose, the reaction rate fell. Introduction Virtually all of the complex biochemical reactions that take place in animals, plants, and micro organisms are regulated by enzymes. Most enzymes are Proteins. Each enzyme is able to catalyse only one type (or a small number) of chemical reactions. Enzymes may only catalyse reactions which can happen naturally; the substrates do not require the enzyme but the reaction is much faster in its presence. In 1965 a theory was created by biologists describing an 'induced fit' - where the structure of an enzyme is altered by its substrate, by the movement of charges and hydrophobic/hydrophilic interactions, so the substrate fits perfectly on the active site in such a way that its reaction can be catalysed. Once the reaction has ended, the enzyme returns to its original shape which uses up the least energy to hold together. It was the work by chemists on the strong and weak chemical bonds which allowed for this theory to be created. ...read more.

Middle

The reaction mixture is made up using 10ml of buffer of a particular pH with 5ml 10 Moll��Hydrogen Peroxide. For each experiment 1ml Yeast solution is added to start the reaction. Experiment 3 - The Effect of Variation of Temperature To perform this experiment the use of a water bath is employed to raise the temperature. To lower the temperature, cooled water or ice is used in a basin. The conical flask is partially submerged in either to cool/ heat the reaction mixture. The reaction mixture is made up of 10ml pH 7 buffer mixed with 5ml 10 Moll��Hydrogen Peroxide. 1ml Yeast solution is used to start the reaction. Only temperature is altered in the experiment. Temperatures of 0, 10 ,20, 30, 40, 50 and 60�C are used. Experiment 4 - The effect of inhibitors Using the same apparatus as in experiment 1 and 2, a reaction mixture of 9ml pH 7 buffer, 5ml 10 Moll��Hydrogen Peroxide and 1ml inhibitor solution is produced and reacted with 1ml Yeast solution. Inhibitor solutions of different concentrations are used; 1, 0.75, 0.5, 0.25 and 0.1 Moll��solutions are used. The inhibitor I chose was Copper (II) Sulphate solution. Results Experiment 1 - The Effect of Variation of Enzyme Concentration Time (s) Volume of Oxygen Produced (cm�) 0 Yeast 1 cm� Yeast Solution 2 cm� Yeast Solution 3 cm� Yeast Solution A B C Av A B C Av A B C Av 10 0 1 1 0.5 0.8 2.5 4 2 2.8 4 5 ...read more.

Conclusion

There would have been some small inaccuracies in the results due to occasional poor washing of the apparatus after use. For example when the conical flask was not washed out several times some Yeast/Catalase would remain on the bottom. This could be seen when small bubbles formed when Hydrogen Peroxide was added (this was performed as an experiment after only two cleans of the conical flask - a deliberate error to find out how thorough a wash was required). For all measurements of solutions, different sizes of pipettes were used. There were some inaccuracies in the actual measurement to the liquids (human error) due to poorly checking the position of the bottom of the meniscus against the line of the volume required. Only two granulated pipettes were required, a 1ml and a 10ml pipette. Since many chemicals were used, each time a pipette was used it had to be washed out several times with distilled water. Before the pipette was then reused, it had to be washed out with the chemical it was going to measure. These procedures insured no contamination and inaccuracies in many of the measurements by systematic error. Once the syringe containing the Yeast solution was depressed, the conical flask was not moved e.g. to swirl the contents around, since this would create too many inaccuracies such as the length of time and force with which the flask was swirled. The yeast solution was made up each day and disposed of afterwards to ensure a constant 4% solution. ...read more.

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