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An investigation to find out how surface area affects the action of the enzyme Catalase.

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An investigation to find out how surface area affects the action of the enzyme Catalase Background: An enzyme is a biological catalyst, or a substance that acts as a catalyst in a living organism, regulating the rate at which chemical reactions take place, without itself being altered in the process. The biological processes that occur within all living things are chemical reactions, of which most are regulated by enzymes. Without these enzymes, many of these reactions would not occur at an acceptable rate. An enzyme will only work with one type of substance or group of substances called the substrate, to catalyse a certain kind of reaction. Only a certain region of the enzyme, called the active site, binds to the substrate. The active site is a groove or pocket formed by the folding pattern of the protein. An enzyme is a three dimensional structure, together with chemical and electrical properties of the active site, it permits only a particular substrate to bind to the site. These factors determine the enzyme's specificity. Because the enzymes are not used up in the reactions they catalyse and can be used over and over again, only a very small amount of an enzyme is needed to catalyse a reaction. A reaction will reach its maximum velocity when all the active sites of the enzyme molecules are engaged. A single enzyme can convert around 1000 substrate molecules per second. The rate of reaction will increase as the substrate concentration is increased. When all the active sites available are engaged, the enzyme is said to be saturated. The rate of reaction is determined by the speed at which the active sites can convert substrate to product. In this instance Hydrogen Peroxide to Water and Oxygen. Hydrogen peroxide - symbol equation H2O2 - is a substance that is produced by numerous metabolic reactions. This toxic waste created extensively in mammalian tissues is catalysed by Catalase. ...read more.


If there are sufficient substrate molecules to occupy all of the enzymes' active sites, the rate of reaction is unaffected by further increases in substrate concentration as the enzymes are unable to break down the greater quantity of substrate. * To control the substrate concentration, I will use 40cm� of substrate in each experiment. To ensure that this was measured precisely, I used a measuring cylinder to gauge precisely 40cm� of substrate. * Inhibition - Inhibitors compete with the substrate for the active sites of the enzyme (competitive inhibitors) or attach themselves to the enzyme, altering the shape of the active site so that the substrate is unable to occupy it and the enzyme cannot function (non-competitive inhibitors). Inhibitors therefore slow the rate of reaction. They should not have affected this investigation, however, as none were added. * Enzyme Concentration - Provided there is an excess substrate, an increase in enzyme concentration will lead to a corresponding increase in rate of reaction. Where the substrate is in short supply (i.e. it is limiting) an increase in enzyme concentration has no effect. This last point will not be a problem, as 40cm� of substrate is sufficient to occupy all the catalase molecules from the potato. This factor - enzyme concentration - will help me to answer my aim, as I am trying to find how the surface area and therefore the concentration of the catalase in the substrate affect the rate of reaction. I varied the enzyme concentration by altering the surface area of the potato cuboids that contain the Catalase, in the reaction, the greater the surface area of the potato, the greater the enzyme concentration. The concentration of the catalase molecules in the hydrogen peroxide solution is determined by the amount of molecules per a certain measure. So as the hydrogen peroxide remains constant at a volume of 40cm�, the concentration of the catalase increases as more catalase is present in the H2O2. ...read more.


the gap between the line for 64 and 100cm� is disproportionately large in comparison to the difference, as the increase in reaction rate in relation to surface area is one of exponential increase. This also shows my prediction is correct. A problem I encountered was that I used too much substrate, as the reaction did not finish within an acceptable time limit, or in the time that I had to carry out all the experiments. As there was so much substrate (hydrogen peroxide) it did not all get reacted with the catalase; by using a lesser amount of substrate the catalase would have catalysed the substrate faster. The reaction rate would have remained the same, but oxygen production would finish a lot sooner, and would not reach the same level as when I used 40cm�. I think an acceptable volume of substrate to use would be 5cm�. My results would look like this (5cm� H2O2): Not like this (using 40cm� H2O2): Another factor that may have affected the results was where the potato came from, because if I used a strip of potato from the centre, rather than the edge, there may have been more catalase present. This could account for the anomaly in results at 40cm�. For all the other results, I may have used potato from the edge, then for this reading I may have used potato from the centre. I do no know if this is true, but it is a possibility. One problem with the method of gas collection was that I had to fill the cylinder with water, and then put it into the trough. Sometimes a small amount of air was left in the tube; this would have created a bias result. To over come this I could have used a syringe to collect the gas, but I did not have the resources available. Overall I feel that I answered my aims conclusively and I feel that my prediction was correct to a large extent, although due to inaccuracies in my results I cannot draw totally complete conclusions. ?? ?? ?? ?? Biology.doc Toby Parnell 11G Page: ...read more.

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