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A Plan of an Experiment to See the Effect of Varying Concentrations of Hydrogen Peroxide on Yeast.

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A Plan of an Experiment to See the Effect of Varying Concentrations of Hydrogen Peroxide on Yeast I have been assigned the task of viewing the results of varying concentrations of hydrogen peroxide (H2O2) on yeast. I will do this by placing varying concentrations of H2O2 into a constant amount of yeast, then I will measure the amount of O2 produced (every 10 seconds) and plot a line graph for each concentration. Using the immediate gradient for the initial rate I will then use these amounts and plot another graph to show initial rate of reaction. Enzymes work as follows: Active Site = Enzyme Substrate Enzyme Substrate Enzyme Products Complex The enzyme joins with the substrate in an area called the active site ( ) this is where the enzyme works. At the active site the enzyme forms temporary bonds with the substrate these bonds hold the substrate in position while the enzyme works. An enzyme lowers the activation energy of a reaction. This means that instead of needing a kick start i.e. some heat, the enzyme lowers the energy needed to start the reaction, so the reaction takes place there and then. This can be seen in the graph below: Using my AS Biology Text Book and my existing scientific knowledge I will now make a well guided prediction. ...read more.


Temperature will be controlled by heating the yeast in a water bath. I will only remove the yeast from the water bath seconds prior to inserting the hydrogen peroxide. This will reduce the heat loss keeping the temperature constant. pH will be controlled by the addition of a buffer. This will keep the pH at a constant amount. Enzyme Concentration this will be kept constant by me adding the same amount of yeast each time. This will be 5cm3. This will keep the enzyme concentrations correct and therefore constant. The variable which I am investigating is Substrate Concentration I will be measuring the effects of this by using 6 concentrations, 0.0, 0.2, 0.4, 0.6, 0.8 and 1.0moldm-3. Enzyme Inhibitors are substances which slow down the enzyme process. Competitive inhibitors attach themselves to the active site of the enzyme. These can stay there forever (irreversible) or they can leave (reversible). Uncompetitive inhibitors occupy other parts of the enzymes distorting the shape of the enzyme and therefore the active site distorts rendering the enzyme either permanently unusable (irreversible) or temporarily unusable (reversible). They are pretty hard to stop but unless I add an unknown substance there shouldn't be any inhibitors. In this experiment I will use 6 concentrations: o 0.0moldm-3 o 0.2moldm-3 o 0.4moldm-3 o 0.6moldm-3 o 0.8moldm-3 o 1.0moldm-3 I will create the above concentrations using serial dilution, the following table is the amounts used to create each concentration: Addition Concentration (moldm-3) ...read more.


I will take a reading at 10, 20, 30, 40, 50 and 60seconds. I will then take a new test tube and place 5cm3 of yeast into it, place the bung on it, insert 1cm3 of the concentration used and time appropriately. I will repeat the above experiment 3 times per concentration for each of the 6 concentrations. I will the plot the average of the results onto the first standard graph of concentration of H2O2 against O2 produced placing each line on the same graph. Next I will take the gradient for its initial rate of reaction, and plot a second graph. I will take each concentration 3 times and then average it to obtain accurate results. Accurate results are a necessity for this experiment due to me plotting two graphs. This experiment will obtain accurate results by my very precise serial dilution of the H2O2 and the precise measuring of the amounts of yeast. I will need to use specific safety techniques to make sure I am no risk of injury or death. I will follow the necessary precautions i.e. no running or always tie hair back etc... I will also need to check the hazcards on H2O2 to see if it is harmful or irritant. I will wear goggles and a lab coat at all times. For this experiment I used the following resources: OCR Advanced Sciences Biology 1 ME Class Notes Daniel Rodgers - 1 - ...read more.

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