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Investigating the enzyme Catalase

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Investigating the enzyme Catalase-AS biology coursework Introduction The experiment being carried out will find the effects of the enzyme catalase with different concentrations of substrate. . This enzyme is common in living organisms and its function is to catalyze the decomposition of hydrogen peroxide to water and oxygen. Hydrogen peroxide is a poisonous by product of metabolism, it can kill cells. Catalase from a potato will be used. An enzyme is a protein produced by any living organism which acts as a catalyst in specific reactions without being used up. All cells produce H2O2 2H2O2 � 2H2O + O2 in Metabolism. It is toxic so it is broken down by catalase. The factors that affect the enzymes are: Temperature changes - catalase works well at high temperatures up to 45�C. This is because they gain kinetic energy so the move around faster, more substrates can be broken down in the same amount of time. After then however the enzymes start to denature. At a low temperature the enzymes do not have as much kinetic energy so they don't work as fast. If its higher than 45�C, then the loses its tertiary structure as the bonds holding it together are broken so the enzyme loses its active site shape. pH changes - There is a narrow range of pH's that the catalase can work in. It works well at pH 7. If the pH goes above or below this, there will be a change in the concentration of hydrogen ions. ...read more.


of bubbles in 4th 30s Average number of bubbles 2 cm trial 18 26 23 22 23.7 1 cm trial 25 25 26 24 25 0.5 cm trial 29 34 36 34 34.6 Evaluation of preliminary experiment results The results here do support my prediction but they are not accurate. There is too much variation between the results using the 2 cm pieces (26-18 = 8 bubbles) and the 0.5 cm pieces (36-29 = 6 bubbles). The difference between the average number of bubbles result for the 2 cm and 1cm trial is a lot less then between the 1 cm and 0.5 cm trial. These should be about the same, as the amount of enzymes leaving the potato doubles as the surface area doubles. So the difference between the results showing the average amount of bubbles produced should be consistent but is not, in this experiment. Improvements to preliminary experiment. Counting bubbles accurately in a exact amount of time is hard and makes human error have a bigger impact on the experiment. If volume of oxygen produced is recorded the human error will be smaller. The time before a result is collected should be more than 30 seconds, as this should give results with less variation, as more gas is collected. Error gives a bigger impact on results if a shorter time is used. The result should now be recorded every minute. A inverted burette held with a stand and clamp should be used. As the volume of gas is recorded, a burette is more accurate. ...read more.


The Delivery tube was fixed so it went under and into the bottom of the burette, in a way that no air bubbles get trapped. This is done on a white tile. A 6 cm potato cylinder was cut using a cork borer. 12 0.5 cm cylinders are cut from the 6 cm cylinder. Any skin was cut from the potato to prevent the catalase getting blocked. The pieces of potato were put into the clamped boiling tube containing the hydrogen peroxide. As soon as this was done the bung containing one end of the delivery tube was put on the tube. And then the time was started. After every minute, the amount of gas collected was recorded. This was done by misusing the initial volume of water from the final volume of water. Two repeats were taken out. The last 4 steps were repeated for the two repeats for this concentration, and for the other different concentrations and their repeats. The boiling tube with the required concentration of hydrogen peroxide was clamped. Also the burette had to refitted to let the oxygen out. Prediction A predict that up until a certain point, the volume of oxygen produced will be directly proportional to the increase in substrate concentration. However after this point, the increase in oxygen production will start to decrease. This is because the more substrate molecules, the more the enzymes have to break down, so more substrate molecules are broken down in a certain time. However at a certain point there will not be enough enzymes to keep breaking down more and more substrate molecules in the same time, so the oxygen production won't increase even if the concentration of substrate molecules increase. ...read more.

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