Hydrogen peroxidase coursework

Catalase is an enzyme which is found in most living organisms. It catalyses the decomposition of hydrogen peroxide into water and oxygen. I believe that as the concentration of the hydrogen peroxide (substrate) decreases, the rate of reaction will decrease as well.
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Enzymes such as Catalase are protein molecules which are found in living cells.

Effect of Substrate Concentration on the Rate of Activity of Catalase | Owlcation

They are used to speed up specific reactions in the cells. They are all very specific as each enzyme just performs one particular reaction. Catalase is an enzyme found in food such as potato and liver. It is used for removing Hydrogen Peroxide from the cells. Hydrogen Peroxide is the poisonous by-product of metabolism. Catalase speeds up the decomposition of Hydrogen Peroxide into water and oxygen as shown in the equations below.

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It is able to speed up the decomposition of Hydrogen Peroxide because the shape of it's active site matches the shape of the Hydrogen Peroxide molecule. This type of reaction where a molecule is broken down into smaller pieces is called an anabolic reaction. Add 2cm3 of yeast to one test tube. Use a pipette to measure out the volumes. It is very important to accurately measure the amounts of Hydrogen Peroxide, Yeast and water to ensure a fair test.

Pour the hydrogen peroxide solution into the test tube containing the yeast and immediately put the gas syringe bung on the end of the test tube, at the same time start the stopwatch. The table below shows what amounts of Hydrogen Peroxide and water are needed to make the solutions. Repeat all the tests at least three times so that an average can be obtained. Repeating the experiments several times will help to produce better and more accurate results as any inaccuracies in one experiment should be compensated for by the other experiments.

Note all the results in a table such as the one below. This gives the rate in cm3 of oxygen produced per second, this is because I am timing how long it takes to produce 30cm3 of oxygen. From these results a graph can be plotted with concentration on the x-axis and time taken on the y-axis. I am using yeast catalase as opposed to catalase from apples, potatoes or liver because it is easier to get the desired amount of yeast catalase by simply measuring it off.

Catalase and hydrogen peroxide coursework

To obtain catalase from a substance such as potato would involve crushing it and with that method you would never be sure of the concentration of the catalase. If the catalase was used up then another potato would have to be crushed and this could produce catalase of a totally different concentration which would lead to inaccuracies in the experiment making this an unfair test. To ensure this is a fair test all the variables except for the concentration of Hydrogen Peroxide must be kept the same for all the experiments.

Variables that must not be altered include Temperature, yeast concentration, type of yeast, batch of yeast, volume of yeast, volume of hydrogen peroxide, air pressure and humidity. When measuring the volumes of Hydrogen Peroxide, Yeast and Water the measurement should be taken by looking at the scale at an angle of 90 degrees to it to avoid any parallax error. I predict that as the substrate concentration increases, the rate of reaction will go up at a directly proportional rate until the solution becomes saturated with the substrate hydrogen peroxide.

When this saturation point is reached, then adding extra substrate will make no difference.


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The rate steadily increases when more substrate is added because more of the active sites of the enzyme are being used which results in more reactions so the required 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 are being done at once so any extra substrate molecules have to wait until some of the active sites become available.

All the times are in seconds. The average results are all written down to one decimal place because although the stopwatch gives results to two decimal places it is impossible to get accurate times to two decimal places due to the fact that our reaction times are not fast enough to stop the stopwatch precisely. I then worked out the rates of the reactions with the equation.

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From these rates I was able to plot a graph of the rate of reaction against concentration of Hydrogen Peroxide. If you double the concentration of Hydrogen Peroxide then the rate of reaction doubles as well. I would expect the rate to increase two times if the Hydrogen Peroxide concentration is increased two times because there are twice as many substrate molecules which can join onto the enzymes active sites. There may also be some experimental error which causes the inaccuracies.

This is shown by the gradient of the graph going down. At this point virtually all the active sites are occupied so the active sites are said to be saturated with Hydrogen Peroxide. A disadvantage of using biological catalysts is that they rely on certain temperatures to ensure that they work best. Enzymes in your body work best at 37 degrees centigrade, which is your actual body temperature.

When Manganese Dioxide is added to Hydrogen Peroxide, the Hydrogen Peroxide is begins to break down in to two substances. Hydrogen Peroxide breaks down in to Oxygen and water. To collect data I cannot measure the amount of water produced. This is because it will be very difficult to separate the water produced as it has been dissolved with the hydrogen peroxide. Instead I am going to measure the volume of Oxygen in centimetres cube, as the Oxygen bubbles will not easily dissolve in water.

I am going to measure the oxygen by collecting the gas in a measuring cylinder, which is full of water. The theory is that when the gas goes in to the cylinder by a delivery tube, the oxygen gas pushes out the water. This process is called the downward displacement of water. I have chosen to investigate how the concentration of Hydrogen Peroxide affects its decomposition. Prediction I think that if I increased the concentration of the Hydrogen Peroxide the speed of the reaction will increase. I also think that as I increase the concentration of the Hydrogen Peroxide, more Oxygen will be produced.

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This will happen because the higher the concentration the more easy it is for the Manganese Dioxide to react with the Hydrogen Peroxide. The hydrogen peroxide.

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Ib Bio Experiment on Effect of Substrate Conc on Enzyme Activity

How to cite this page Choose cite format: The hydrogen peroxide. This resulted in more enzyme-substrate complexes formed in the higher concentrations, and less in each decreased concentration.

This supports the Maxwell-Boltzmann distribution curve I referenced earlier. I have drawn a graph based on these average results with a curve of best fit for each concentration that will allow me to identify any anomalies.

Draw a curve of best fit on your graph. From the graph, I can see that as the concentration of hydrogen peroxide decreased, the volume of oxygen produced decreased as a direct result. This is because as the concentration decreased, the number of molecules of hydrogen peroxide also decreased. This decreased the number of particles that could react with each other, and so the number of collisions that reached the activation energy also decreased.

This meant that there were also less successful collisions, and so less enzyme-substrate complexes formed. The final volume of oxygen produced also decreased as the concentration decreased.

This is because fewer overall collisions took place, and so a reduced number of collisions reached the activation energy.