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Hypothesis: Increasing the surface area of the potato cylinders will increase the number of enzymes.

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Hypothesis: Increasing the surface area of the potato cylinders will increase the number of enzymes. This means the rate of reaction will also increase due to the increase in active sites. This also means that doubling the surface area will also double the rate of reaction. Theory The breakdown of hydrogen peroxide by catalase is a catabolic reaction and results in the formation of water and oxygen. The following chemical equation represents this reaction. 2H2O2 2H2O + O2 Catalase is an enzyme, which can be found in potatoes. Enzymes are globular proteins, which are also known as biological catalyst. Enzymes are able to break down molecules because they have a special feature called an active site. This feature enables them to break down molecules with out being effected. This means that that at the end of the reaction there not used up. This active site that enzymes posses has a unique shape which means only one type of substrate can bind to it. When the substrate attaches itself to the enzyme it is kept in place by the R groups of the enzyme. This attachment is known as an enzyme - substrate complex. This interaction between the R group and the atoms in the substrate starts to break bonds in the substrate, causing two or more products to be formed. ...read more.


This is because the more enzymes there are the more active sites there are. This means that more substrate can be broken down at one point in time so the rate is higher. This is true only if there is excess substrate available. If there is a short supply then increase in enzyme concentration has no effect on the rate of reaction. Enzyme concentration will be the independent variable in this experiment. I will vary the amount of catalase by changing the surface areas of the potato cylinders. As potato contains catalase it can be said that the higher the surface area the higher the enzyme concentration. Even though the surface area of the potato cylinders need to be varied the volume and mass needs to be kept constant otherwise the experiment will not fair and no conclusions can be drawn from the results. . The only way this can be done is by starting with a potato cylinder 10mm in diameter and 50 mm in length. This will be the first surface area that will be tested. By getting another potato cylinder 10 mm in diameter and 50 mm in length and cutting it in half to get two cylinders each 25mm in length the second surface area will be gained. From looking at the table on page 8 it is clear that the total surface area of these two cylinders is higher than the surface area of the 50mm cylinder but the volume and mass are the same. ...read more.


As soon as you have added the hydrogen peroxide replace the bung with the manometer and time how long it takes for the manometer fluid to travel up by 5 cm. 12. Repeat step 9 and 10 and work out the average of the three readings. By repeating a surface area (enzyme concentration) several times I can work out the average and minimise inaccuracy. 13. This experiment should be repeated for different total surface areas. The different total surface areas are shown in the table below. (At 0 mm in length no potato will be added to the solution. This will act as a control.) Number of cylinders Length of each cylinder (mm) Surface area of each cylinder (mm2) Total surface area (mm2) Total volume of all cylinders (mm3) 0 0 0 0 0 1 50 1728 1728 3927 2 25 942 1885 3927 3 16.7 682 2045 3927 4 12.5 550 2199 3927 5 10 471 2356 3927 The surface area of each cylinder was found using the following formula: Surface area = 2(?r2) + L?d L= Length (mm) d= Diameter (This is always 10 mm) r= Radius (This is always 5 mm) The total surface area was found by multiplying the surface area of each cylinder by the number of cylinders. The total volume was found using the following formula: Total volume = L?r2 Health and safety * Labs must be worn throughout the experiment. ...read more.

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