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The effect of substrate concentration on Potato Catalase

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The Effect of Substrate Concentration on Plant Catalase Aim The aim of this experiment is to investigate how the concentration of the substrate, Hydrogen Peroxide, affects the rate of a chemical reaction with plant catalase. Hypothesis An enzyme is a biological catalyst, which increases the rate of chemical reactions. Catalase is an enzyme, which occurs in the cells of many living organisms. Certain of the energy releasing reactions in the cell produce hydrogen peroxide as an end product. This compound, which is toxic, is split into water and oxygen after reacting with catalase. Hydrogen Peroxide � Water + Oxygen 2H2O2 � 2H2O + O2 I predict that as the substrate concentration increases the rate of reaction will also increase. At the beginning of the reaction there are lots of substrate molecules around, therefore more active sites can bind with them. This shows how the substrate bonds to the active site of the enzyme: If the substrate concentration is constantly increased, and the enzyme concentration remains constant there comes a point where every active site is working continuously. If more substrate is added the enzyme cannot work any faster, because the active sites are saturated. The substrate molecules have to wait until the enzyme-substrate complex (e-s complex) has released the products before it can enter into the active site. ...read more.


so that the pH remains constant. * Cork borer * Knife * Ruler * 45cm� hydrogen peroxide (1 mol concentration) - substrate for dilution * Distilled water - for diluting the hydrogen peroxide * Monometer tube approximately 3mm in diameter * Monometer fluid * Spring clips - to open and close the monometer, which will bring the monometer fluid back down to its original level when opened. * Wax pencil - for marking a gap of 5cm on monometer above the level of monometer fluid. * 2 syringes 5cm� -to increase the accuracy of measurements * 5 boiling tubes * Rubber bung * Forceps * Sticky labels * 5 Beakers 20cm� * Clamp stand * Digital stop clock - for gathering more accurate results Procedure 1. Consider safety precautions - handle dangerous equipment carefully, wear lab coat and goggles 2. Set up the apparatus as shown below 3. Cut 10 potato discs of 1mm thickness. 4. Get five 20cm� beakers, distilled water and 45cm� hydrogen peroxide to prepare dilutions as followed: 5. Label the beakers with their concentrations 6. Put 5cm� of the first prepared substrate concentration into the boiling tube then add 5cm� of the catalase solution to it. 7. Put rubber bung back onto boiling tube as soon as possible because the reaction begins as soon at the two solutions are combined. ...read more.


There are two anomalies in the results at 4vol and 8vol substrate concentrations. The anomalies could have been due any of the variables not remaining constant. It was difficult to maintain accuracy during the procedure. This was because it had to be repeated so many times. It was quite a long procedure and it had to be done in total 15 times. One variable that may have differed was the thickness of the potato discs. As there were 150 discs it was difficult practically to make sure they were all equal in size. Given the time I had to complete the experiment many of the discs were measured subjectively. The time taken to replace the rubber bung, after the substrate had been added to the potato catalase also affected the reliability of the experiment. Once the bung had been replaced on the test tube the reaction had already begun so the time taken was not measured accurately. I also had to predict the rest of the graph because there were not enough results. This was due to there not being higher substrate concentrations available. This experiment could be improved if there was access to higher concentrations of Hydrogen Peroxide. This would have increased the number of results obtained and therefore increased the range of the graph. This would have shown more patterns in the results, which would have produced a more accurate and successful experiment. ...read more.

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