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Rate of reaction

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Investigation to see the effects of temperature on the breakdown of hydrogen peroxide by catalase Aim The aim of this investigation is to find out the effect of temperature change on the rate of enzyme activity. The enzyme that I will use will be catalase and will measure the rate at which it breaks down hydrogen peroxide at different temperatures. 2 H2O2 � 2 H2O + O2 This reaction emits oxygen what I will use to measure the rate of reaction with the rate of oxygen emitted Background information (for better understanding therefore better investigation) Enzymes- All enzymes are biological catalysts; they lower the activation energy needed for a reaction to start, therefore increasing the rate of enzyme to substrate collisions that have the activation energy needed to start the reaction, more successful collision meaning a higher rate of reaction. Without enzymes chemical reactions would occur too slowly to support life as we know it. This graph shows how enzymes lower the activation energy needed to start a reaction and therefore speedup the reaction because more successful collisions take place. Enzymes work by attaching themselves to their specific substrate to break it down, this also works in reverse. This diagram shows how enzymes connect to their specific substrate threw the active site to produce its product. Factors that effect enzyme activity- The main factors that effect the rate of an enzyme catalysed reactions are- * Enzyme concentration * Substrate concentration * pH level * Temperature Enzyme concentrations- increasing the enzyme concentration will increase the number of enzyme substrate collisions giving a higher chance for successful collisions which therefore will increase the rate of reaction. Substrate concentration- increasing the substrate concentration will increase the number of enzyme substrate collisions giving a higher chance for successful collisions which therefore will increase the rate of reaction. However the rate of reaction will reach its maximum once all enzyme active sites are occupied, so however much the substrate concentration is increased the rate of reaction will stay the same. ...read more.


This can only be achieved by keeping all outside variables constant. The main variables that would affect the results are - Temperature - kept constant room temperature. This temperature will be easiest to keep constant. To increase accuracy all reading will be taking in the same time period to avoided any significant temperature change due to the weather or heating. Enzyme and substrate concentration - will be kept as accurate as possible by the use of a 5cm� syringes to add the substrate and cork borer and razor blade for the enzyme (potato disks) Preliminary results Analysis of preliminary pH level Gradient 5-6 3.0 6-7 10.3 7-8 -7.0 8-9 -6.6 The results from the preliminary showed a clear patter. The highest rate of reaction was at pH 7 with the lowest at the far ends (5, 9). The results correspond with the background information but also give further information from the graphs gradients of the rise of rate of reaction between the pH levels. The highest rise of rate of reaction was from pH level 6-7 what was 10.3, this was the level approaching the optimum pH, around these levels most of the enzymes tertiary structure are becoming more stable The fastest drop of rate of reaction was between pH levels 7-8 what was -7, this is just after the optimum pH level, this would be where most of the enzymes will start having its R groups charge affected by the H ions altering its tertiary structure leading to it becoming denatured. Hypothesis Based on the background information researched, and the preliminary carried out, a fairly accurate prediction of the main experiment would be that the optimum pH level for rate of reaction would be 7. This is there would be hardly any H ions present to affect the tertiary structure of the enzymes. Therefore the rate of reaction will be at the fare ends at pH levels 5 and 9. ...read more.


* Contamination- the investigation was carried out in a college lab so there is a high chance of contamination of the test tubes, razor blades etc... These limitations and sources of error would also affect other candidates performing the same investigation. So to test the reliability of my results taking these factors into consideration I would have to compare them to another candidates results and see if they show the same trends and if the results are in the same regions. The results for the other candidate are:- pH levels Average Time-sec Average 1/T -sec- X10?� 5 161 6.2 6 92 10.8 7 50 20.0 8 72 13.0 9 159 6.2 My results:- pH levels Average Time-sec Average 1/T -sec- X10?� 5 154 6.5 6 103 9.7 7 49 20.0 8 68 14.0 9 170 5.9 As you can see both sets of results are very alike in trend and region of recordings. However this is not a definite conclusion that the results are 100% accurate as there still could be a chance that both sets of results are wrong. But however this being very unlikely, the results reliability does go up with the comparison with the other set of results. The investigation in a whole was to the best level it could be and the results themselves were to the best accuracy giving the circumstances. However if the investigation was to be carried out again, all methods would be kept the same but with only 2 changes to the equipment list:- instead of using a monometer a gas pressure sensor would give more accurate readings and sort the problem of oxygen escaping. Also instead of using potatoes as the source of catalyse, catalyse solution could be used in different amounts. This would solve the problem of the variation on potato thickness and density. Sources I used I researched and used information on enzymes from the following sources:- OCR Philip Allan foundation unit book - Planning www.wikipedia.com - Planning some pictures/diagrams used were obtained from Google images - Planning ?? ?? ?? ?? Osman Shariff Student No.: 20063301 ...read more.

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