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An investigation into what happens when hydrogen peroxide is broken down by an enzyme found in yeast called catalase

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The effect of different substrate concentrations on the rate of reaction. My aim is to investigate what happens when concentration of Hydrogen Peroxide is changed and how it affects the rate of reaction when it is broken down by the enzyme catalase (H2O2 --> 2H2O + O2) Scientific knowledge. Enzymes are biological catalysts, regulating the rate at which chemical reactions take place without the enzyme being altered in the process. Enzymes bind temporarily to one or more of the substrate molecules of the reaction they catalyse. Enzymes work by lowering the activation energy required for a reaction to proceed. In order to do so, and enzyme molecule must unite - even if very briefly - with the substrate molecule(s). Enzymes are able to do this because an area of their structure matches to the substrate. This area is called the active site and is complementary in shape, charge and hydrophobic/hydrophilic areas. The substrate attaches to the active site by a random collision but is held briefly by hydrogen bonds, ionic and hydrophobic interactions. Because the substrate must fit into the active site the mode of enzyme action is comparable to a lock and key. Sometimes the substrate attaches to the active site and triggers a shape change in the enzyme molecule which improves the fit further and causes the reaction to occur. This is referred to as induced fit. The requirement for complementarity in the configuration of substrate and enzyme explains the remarkable specificity of most enzymes. ...read more.


3) Finally, the curve levels out to show all hydrogen peroxide molecules have reacted; there are no more left. Signalling an end to the reaction. Equipment Choices Apparatus No./Vol required Purpose Reason for Choice Conical Flask (100cm3) 1 To contain potato tubers and H2O2 where reaction will take place. Easy to use, bung fits in perfectly. Yeast Solution 60cm3 Contains the enzyme catalase. Good source of catalase. More reliable than using potato tubers. Clamp stand 1 To hold gas syringe in place. Saves you having to hold it in place. Delivery tube 1 To allow oxygen to travel through to the gas syringe, allowing you to measure the amount produced. No oxygen is lost out into the surrounding atmosphere. Gas Syringe (100cm3) 1 Measures how much oxygen has been produced. Suitable measuring method. Large enough capacity. Easier to use than a measuring cylinder as water displacement doesn't have to be calculated. Hydrogen Peroxide 50 cm3 of each of 6 concentrations. Substrate Good source of substrate. Stop Watch 1 Used to calculate time. Reliable source of time keeping. Bung 1 Stops oxygen from escaping out of the conical flask. Air tight. 5ml syringe 1 Used to measure out dilutions of hydrogen peroxide. Easy and safe to use. Distilled Water 100cm3 Used to dilute hydrogen peroxide concentrations. Doesn't contain any impurities which may react with the substrate solution. Table of Concentrations Concentration (vol) Volume of H2O2 (cm3) Volume of distilled water (cm3) 20 5 0 16 4 1 12 3 2 8 2 3 4 1 4 0 0 5 Method 1. ...read more.


Some oxygen could have been lost when having to put bung on top of flask. Also delay in time keeping as bung had to be put on top of flask before I could start the stop watch. Make sure there are enough syringes or wait until one is available. Inaccurate observation. Anomalous results recorded in highest concentrations because reaction was happening so fast. Work in pairs, so readings can be observed more accurately. Repeats taken from other people. Results were taken from numerous amounts of people. Everyone has made their own personal errors, making results more unreliable. All repeats should be done yourself, therefore you know what exactly what errors you have made. My results were fairly accurate, most errors were due to lack of observation and silly mistakes. A few anomalous results have arisen. These are located in the highest concentrations. The speed of the reaction was so quick that I could have easily misread the correct volume of oxygen produced. Taking repeat results from other people is one of the major limiting factors. As one persons mistake can lead to the average results graph looking terribly wrong. In conclusion, I have proved my hypothesis to be correct by using both scientific knowledge of enzymes and conducting a well planned experiment. My results graph looks very similar to my predicted graph again showing my results were reliable. Thus explaining how the rate of reaction is affected during the breakdown of Hydrogen Peroxide by the enzyme catalase. ?? ?? ?? ?? AS Biology Coursework Katie Man 1 ...read more.

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