An investigation into the effect temperature has on the activity of the enzyme catalase in the breakdown of hydrogen peroxide into water and molecular oxygen

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An investigation into the effect temperature has on the activity of the enzyme catalase in the breakdown of hydrogen peroxide into water and molecular oxygen

.....In an enzyme-catalyzed reaction, the substance to be acted upon binds reversibly to the active site of the enzyme. One result of this temporary union is a reduction in the energy required to activate the reaction of the substrate molecule so that the products of the reaction are formed.

                                                       2H2O2 =2H2O + O2

Catalase is an enzyme present in the cells of plants, animals and aerobic (oxygen requiring) bacteria. The enzyme catalase decomposes hydrogen peroxide (H2O2) into water (H2O) and oxygen (O) gas.  

Although enzymes are sensitive molecule, enzymes are very specific; they are made up of globular protein which had polypeptide chains. Enzymes work in a reaction by fixing themselves to substrates, these reactions can be described as catabolic or anabolic. The theory behind enzyme reactions is often described as ‘lock and key’. This theory relies heavily upon the idea that the protein which the enzyme is made of keeps its specific shape. Catalase has a narrow range of conditions under which it can function properly. These conditions are called variables. These variables affect the enzyme kinetics. The independent variables in this reaction are substrate concentration, temperature, PH and the enzyme concentration.

Independent variable: temperature

However in my experiment I am going to investigate the affect temperature has on the rate in which the enzyme catalase reacts with hydrogen peroxide to produce hydrogen and oxygen.

 

In general, chemical reactions speed up as the temperature is raised. When the temperature increases, more of the reacting molecules have the kinetic energy required to undergo the reaction. Enzyme catalyzed reactions also tend to go faster with increasing temperature until a temperature optimum is reached. Above this value the conformation of the enzyme molecule is disrupted. Changing the conformation of the enzyme results in less efficient binding of the substrate. At this point the enzyme is denatured –it not longer functions as a catalyst.

I’m going to do a series of preliminary results to test at which temperature the enzyme is still active, because the temperature at which the enzyme doesn’t produce any oxygen are futile. Through my preliminary results I discovered that there was little or no oxygen produced before 5 degrees centigrade and above 70 degrees centigrade showing that there is little enzyme activity and a virtual non existent rate of reaction. So I have chosen to set the independent variable at 5 degrees centigrade intervals between 5 and 60 degrees centigrade. I am also going to repeat the same temperatures three times and attain an average result so that if any anomalies occur they will not be mistaken for an actual rate of reaction at this temperature.    

Dependant variable: oxygen

The amount of oxygen produced will be used to indicate catalase activity and how this is affected by the different temperatures. If the hydrogen peroxide is broken down into water and oxygen then the catalase has been active. If no water or oxygen is produced then you know that the catalase activity has been stopped. Therefore, to test for catalase activity you can test for the presence of oxygen. I will obtain the enzyme catalase from potato.

Variables which have to be kept constant:

In my experiment I have to choose the substrate concentration. Substrate concentration affects the rate of reaction up to a certain point. The higher the substrate concentration, the faster the reaction, but only up until a ‘saturation’ point. After that, there’s so many substrate molecules that the enzymes have about as much as they can cope with, and adding more makes no difference/  Eventually the maximum rate for that reaction will be achieved and further increases in substrate concentration will have no effect.

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 I have a choice of using either a concentration of 10% hydrogen peroxide or 20% hydrogen peroxide. I tested both of these substrate concentrations and found that visibly the 20% concentration of hydrogen peroxide produced a higher rate of reaction with in a time period that the 10%. This was due to the 10% containing less substrate molecules with the solution which lowers the chance that they will bind with the catalase active site and react and produce oxygen. I have chosen the 20% because in my experiment I think that this will be more accurate to measure ...

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