Reaction of catalase with hydrogen peroxide AIM: I aim to find the rate of reaction between catalase and hydrogen peroxide. Enzymes such as Catalase are protein molecules that are found in living cells. They are used to speed up specific reactions in the cells. Each enzyme just performs one particular reaction so they are all very specific. Catalase enzymes found in living cells e. g. in yeast, potato or liver, speed up (in our case) the breaking down of hydrogen peroxide. The lock and key analogy… The lock is the enzyme and its active sight is where you put the key in.
The key is like the substrate that comes and bonds to the active site or the key that fits into the lock. [pic] The collision theory The collision theory explains rates of reaction in terms of the motion of particles in the reactants. For a reaction to happen the reactant particles must collide. Only a certain amount of the total collisions cause chemical change; these are called successful collisions. The successful collisions have enough energy at the moment of impact to break the existing bonds and form new bonds, therefore leading to the products of the reaction Temperature. At a higher temperature, reactant particles are moving faster with greater average kinetic energy. Therefore more of them collide with enough energy to cause a successful reaction. -Concentration. At a higher concentration, there is a greater chance of reactant particles colliding with each other with enough energy to cause a successful reaction. Rate of reaction is directly proportional which means if you double the concentration it will double the rate of reaction. -Surface area. Smaller particles, e. g. in powders have a much greater surface area than lumps or rystals. With a greater surface area, more collisions can take place. Rate of reaction therefore doubles if the surface area of the reactant particles double. Hypothesis I predict that as the substrate concentration of hydrogen peroxide increases the rate of reaction will also increase. I also predict that as the substrate concentration decreases, it will take more time for the oxygen to be produced. However when the enzyme molecules go beyond the number of substrates available in hydrogen peroxide the reaction will no longer increase.
This is due to there being more substrate molecules to react with the active site, resulting in more frequent successful collisions. Consequently, when the hydrogen peroxide particles break down faster more oxygen and water can be released meaning a faster reaction can take place Safety rules Wear eye protection (goggles) and cover clothing when using hydrogen peroxide (apron). Wash splashes of catalase or hydrogen peroxide off of the skin immediately. Take care inserting the bung in the conical flask- it needs to be a tight fit, so push and twist the bung in with care.
Preliminary work When beginning my experiment I carried out a preliminary test to see what worked best, and gave the most accurate and reliable results. After my preliminary work I decided that I would use the concentrations 1cm? , 2cm? , 3cm? , 4cm? and 5cm? as they gave the most accurate reliable results. Equipment – 1 x 250ml conical flask- to hold the solution – 1 x bung with delivery tube- bung to make sure no oxygen can escape and delivery tube for the oxygen to travel through. – 1 x 100ml measuring cylinder- to contain and measure accurately the distilled water. 1 x 25ml measuring cylinder- to measure accurately the catalase solution – 1 x 10ml measuring cylinder- to measure accurately the hydrogen peroxide – 1 x plastic tub – to contain the distilled water – 1 x goggles- for safety purposes. – 1 x 10ml syringe- to insert the hydrogen peroxide into the conical flask. – 1 x stop watch- to measure accurately the time it takes for the reaction to take place. – Catalase liver solution- the solution we will be investigating – 20 volume of hydrogen peroxide- to cause the reaction that we will be investigating – Distilled water- to dilute catalase.
We are using distilled water to make sure all the water has the same pH, ensuring accurate results. – Cardboard rectangle- to ensure no water escapes when tipping the 100ml measuring cylinder into the plastic tub. METHOD 1. Collect all the equipment and set it up in a clear working space. 2. Fill the plastic tub about halfway to the top, with tap water. 3. Place the cardboard square on top of the 100ml measuring cylinder, making sure no water can get out; flip it over into the tub trying to loose as little water as possible. Your partner must keep the cylinder steady and vertical. 4.
Using the 25ml measuring cylinder, measure 5cm? of catalyse, and pour this into the conical flask. As we are using 5cm? of catalase at the moment we do not need to dilute it, as the total solution is 5cm?. So seal your conical flask with a bung. (To make things easier you should collect the catalase and hydrogen peroxide in two beakers so that you find it easier to measure accurately from. ) 5. Using your syringe you measure 5cm? of hydrogen peroxide. Then place the syringe into the hole in the bung. 6. Now place the delivery tube that is attached to the bung underneath the 100ml measuring cylinder in the water. . Once this is done, you are ready to time your reaction. Push down on the syringe, adding the hydrogen peroxide to the catalase solution, and start your stopwatch. You should time how long it takes for the amount of water to reach 100ml to 0ml. When you change the concentration for example to 3cm? of catalase, you will then need to use distilled water to create the total amount of 5cm?. So therefore you would have to add 2cm3 of distilled water to create the total amount. You will do this for each of your 5 chosen concentrations.
You should repeat the experiment for each concentration three times so that it will give you accurate reliable results and so that an average can be obtained!!! Variables When carrying out my experiment, I will come across variables that may affect the results of my experiment. The variables are as follows: – Independent variable: this is the only feature that will change throughout the experiment. I will change the concentration of catalyse by changing the amount of water added, because I am investigating whether different concentrations of catalase, affect the rate of decomposition of hydrogen peroxide.
The rate steadily increases when more substrate is added because more of the active sites of the enzyme are being used; this results in more reactions so the amount of oxygen is made more quickly. Once the amount of substrate molecules added exceeds the number of active sites available then the rate of reaction will no longer go up. This is because the maximum number of reactions has taken place and no more active sites are available. – Dependent variable: this is variable is the one I am measuring, so in this experiment the dependent variable will be the time taken to release 100cm3 of oxygen in seconds.
The rest of my variables need to be controlled and monitored so that they don’t affect the results of my experiment. I will keep all theses variables the same throughout my experiment. – Controlled variable: I will keep the pH balance of the water the same. If I use a different pH with each experiment, this will mean the reaction will not be able to take place. As when an enzyme exceeds its maximum pH balance it will begin to denature, therefore meaning no reaction can take place. I will monitor this by using distilled water with each of my experiments, as distilled water has a pH of 7.
I will also use distilled water in my catalase solution, so that all experiments use a pH of 7. – Controlled variable: I will keep the temperature of my catalase solution the same throughout all my experiments. A higher temperature will make the molecules separate and move around faster. It will give them more energy to create more successful reactions. Therefore increasing the rate of reaction. So, a lower temperature will slow the speed at which the molecules move and decrease the number and strength of collisions. – Controlled variable: I will keep the concentration of hydrogen peroxide the same.
Oxygen is given off much faster if the hydrogen peroxide is concentrated than if it is dilute. The higher the concentration the quicker the rate of reaction, this is because there are more hydrogen peroxide molecules, which increases the possibility of a successful reaction. Therefore increasing the rate of reaction. – Controlled variable: I will keep the total amount of catalase solution and total volume of hydrogen peroxide the same throughout, maintaining a total amount of 10cm3. If the overall volume of the solution is different then this will affect the rate of reaction giving inaccurate unreliable results. Result table Volume of catalase |Volume of h20 |Volume of 20V h202 |Time taken for 100cm3 to be related (Sec) |Average |Average rate of | |solution (cm3) |(cm3) |(cm3) | |(cm3) |reaction (100/s) | | | | |1st | |5 |4. 99 |4. 73 |4. 53 | |4 |2. 5 |2. 70 |2. 66 | |3 |1. 92 |1. 88 |1. 84 | |2 |1. 19 |1. 18 |1. 16 | |1 |0. 91 |0. 87 |0. 87 | From these rates I was able to plot a graph of how concentration of catalse affected the rate of reaction. (Refer to hand drawn graph)
Conclusion From my graph I conclude that most of my results were quite accurate; as my line of best fit runs through two of my error bars and is relatively close to the other two. For four out of five of my results the error bars are small which means I carried out my experiment carefully with minimal mistakes. This means that my results are accurate and reliable. However, my fifth error bar is exceptionally far out from my line of best fit. The error bar is also large which means that the experiment was not completed with enough accuracy or something went wrong whilst carrying out the experiment.
Things that could have affected the result for 5cm3 are: Human error- I could have made an error when taking the readings and/or I could have inaccurately stopped the stop watch. Contamination- if the equipment hadn’t been sufficiently cleaned after each experiment then there could have been cross contamination of the solutions. This would affect the overall outcome therefore leading to unreliable results. Fault in equipment- there could have been a fault in the equipment that we used to carry out the experiment.
However this probably wasn’t the case the reason for that being that all the other four concentration results came out accurate and the same equipment was use throughout the experiment. Overall I believe that my results that I gathered are reliable and accurate because my line of best fit goes through or very close to all the error bars except one; which was most probably due to human error or cross contamination of solutions as a result of unclean equipment. Now looking at my graph I can see that the results I got for the concentration 5cm3 was an outlier.
Therefore if I was to do this experiment again I would repeat the experiment for that concentration. Evaluation I think the good points of my experiment were that I took care and precision with measuring out all the different components, I also made sure I collected the results as precisely as possible to ensure I got the most accurate reliable results. I thought another good aspect of my experiment was that I handled the hydrogen peroxide carefully and had no spillages. This made sure that I was safe at all times. I think the bad point of my experiment was that I was unable to control one of the variables which was temperature.
The experiments were carried out at room temperature, but this temperature wasn’t accurately constant because there are many factors that could affect the temperature of the room, e. g. a window being opened, heating being turned on. The temperature will affect the rate of reaction. . A higher temperature will make the molecules separate and move around faster. It will give them more energy to create more successful reactions. Therefore increasing the rate of reaction. So, a lower temperature will slow the speed at which the molecules move and decrease the number and strength of collisions.
If I was to carry out this investigation again I would use a gas syringe to get more accurate results. The gas syringe has marks along its length which allow the volume of collected gas to be measured. By using this instead of reading from the 100ml measuring cylinder it would give more reliable results. Another thing I would change would be the amount of times I carried out the experiments for the different concentrations. I would repeat the experiment 6 times each, this is double amount of times I repeated my experiments in this investigation. The more times I repeat the experiment the more accurate my average rate of reaction would be.
I would also use catalase from the same liver. Different samples of catalase would cause negative variation in my data which would affect my overall result. If I controlled this factor by using catalase from the same liver it would give me more accurate reliable results. In conclusion I have enjoyed this investigation and have learnt a lot about rates of reaction and how different factors and variables can affect them. Ellie Gibbons. 6096 GCSE biology coursework ———————– 2H2O2 CATALASE 2H2O + O2
