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Effect of enzyme concentration on initial rate of reaction

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Effect of enzyme concentration on initial rate of reaction The objective of this experiment is to determine how differentiating the concentration of the enzyme catalase affects the initial rate of reaction, in the decomposition of Hydrogen Peroxide (H2O2) The equation of this reaction is: Hydrogen Peroxide(aq) --> Water(l) + Oxygen(g) 2H2O2(aq) + catalase(aq) --> 2H2O(l) + O2(g) The source of the enzyme Catalase in this experiment will be yeast, specifically the Saccharomyces Cerewisea strain, as it is easy to obtain and very safe with no harmful effects to the environment. The technique used to obtain a set of results will be the downward displacement method, where evolved oxygen product from the reaction is passed through a delivery tube and into a water filled burette, pushing the water out of the burette, leaving obtainable results of Oxygen collected. These results will be taken every 5 seconds for two minutes and will give the rate of reaction. My Equipment will be: * Burette * Side-arm Conical Flask * Bung * Tubing * Yeast * Hydrogen peroxide * Water Bath * Water/Margarine Tub * Distilled water/pH7 buffer * Stopwatch I chose to have a burette to collect the evolved Oxygen, as it has a great degree of accuracy. The gas can be measured to 0.05ml or 0.5cm3. I chose to have a side arm conical flask to provide a source for the evolved oxygen to travel through easily. ...read more.


quickly into the side-arm conical flask, and then the 5ml yeast into the same flask, and quickly bung the top. * Measure the oxygen that has evolved every 5 seconds for two minutes, as to gain a value for the initial reaction. * If reaction too fast, half the concentration of hydrogen peroxide (to 10, then 5vols). * Repeat this for the 5 specific temperatures. Precautions: It must be assured that all equipment is washed between experiments where variables are changed, such as the conical flask, graduated pipette etc. also, making sure that they are dried thoroughly is important as any excess water could increase the dilution of the reactants and affect the results. It is also imperative that the stopwatch is started exactly at the same time in each experiment; as soon as the bung is put in. There are a couple of minor safety issues that must be addressed to assure 100% safety. Hydrogen peroxide can be corrosive, and can act as an irritant to the skin, eyes and clothing if spilled and not washed off thoroughly. All enzymes are potential allergies and can irritate membranes found in the eyes nose, or any other cavity. They can also cause asthmatic attacks. Spills of any substance should be washed immediately to obtain the safe environment. A lab coat and goggles should be worn to ensure these safety conditions, however inexplicit they may be. ...read more.


33.4 33.0 33.7 45 32.1 31.7 32.7 50 30.5 30.1 30.8 55 29.5 29.1 29.6 60 27.6 27.4 27.8 This also gave relatively similar to the above experiments but seems a little bit slower. However, it cannot be ruled out until the graph is completed. The last temperature to be tested was 50�C The results are below: Time (seconds) Burette reading (test 1,2,3) Average O2 evolved (cm3) 0 49.5 49.3 49.1 5 47.0 46.6 46.8 10 44.5 44.2 44.3 15 43.1 43.0 43.0 20 41.2 41.2 41.0 25 39.2 38.8 38.9 30 38.0 37.7 37.6 35 36.7 36.4 36.6 40 35.4 35.2 34.8 45 34.1 33.8 34.0 50 32.7 32.4 32.6 55 31.4 31.1 31.2 60 30.7 30.2 30.4 Once again, these resultsare similar to the above, so will again be determined via the graph. Method final experiment: * Set up the apparatus like in the diagram drawn * Place 5ml Yeast containing Catalase and 10ml hydrogen peroxide in water bath (in different vessels), which will be at the specific optimum temperature. * Mix the hydrogen peroxide (10ml/5vols) quickly into the flask containing yeast (5ml), when at required temperature, and bung the top. * Measure the oxygen that has evolved every 5 seconds for two minutes, after the first bubble has evolved as to gain a value for the initial reaction. * Repeat this 3 times for the specified enzyme concentrations, and work out the rate of reaction for each, and then an average for each concentration. ...read more.

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Here's what a teacher thought of this essay

3 star(s)

*** Plan and initial experiments only. This mark is awarded only for the planning section.
The inclusion of many different trial experiments means that this experiment has been thoroughly planned experimentally to find the optimum values for the temperature and concentration of Hydrogen Peroxide.
The hypothesis is testable and is explained using relevant biological background material. The key variables are considered well.
To improve:
The inclusion of more relevant background material to inform the plan would be helpful. The material from textbooks or websites should be referenced at the end.
The risk assessment is not adequate to be awarded marks under the newest marking schemes and needs to considered much more carefully.
The writer needs to ensure that all graphs and table headings are fully labeled with a heading and unit. This should also include sketch graphs used to illustrate a point.

Marked by teacher Stevie Fleming 29/05/2013

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