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Investigating into how the surface area of a potato can affect the rate of reaction of catalase

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Investigating into how the surface area of a potato can affect the rate of reaction of catalase Introduction Catalase is an enzyme found in plant cells (e.g. potatoes) and in tissues of most of the living organisms. Hydrogen peroxide is a metabolic by product in the cell which is converted to water and oxygen by catalase present within the peroxisome of the cell. The hydrogen peroxide needs to be broken down because it is poisonous. 2H2O2 O2 + 2H2O Hydrogen peroxide Oxygen Water Catalase in an enzyme, which is a tertiary protein and has an active site in it to which a substrate can bind forming an enzyme substrate complex. When an active site of an enzyme has a specific shape, the substrate in which it has to bind with should also have a complementary shape, then only they can bind. This type of reaction is known as the lock and key theory� where the lock represents the enzyme and the key represents the substrate. Sometimes, the active site of the enzyme slightly changes shape to allow a substrate to fit in. this reaction is known as the Induced fit theory�. In both reactions, the substrate that enters the active site is broken down into two or more products. In order for the reaction to take place more easily, the enzymes have to lower their activation energy. Throughout the reaction, the shape of the enzyme and its active site doesn't shape. Induced fit theory� Lock and key� Image�- Google image- 'enzymes lock and key theory' Image�- Google image- 'induced fit' 7Factors affecting the rate of an enzyme reaction:- * Temperature * Concentration of catalase * Surface area * Concentration of substrate * pH * Enzyme inhibitors How temperature affects rate Rate of reaction at low temperature will be slow. The collision between the substrate, molecule and the active site may not be so often. ...read more.


Make sure that the size of the cork is just enough to close the boiling tube tightly and use vaseline to prevent gas from escaping. > Set up the clamp stand and add boss head to it, then attach the gas syringe to the boss head. > Cut a potato using a borer to have uniform lengths and place them on a white tile. > Take three equal lengths of the potato and by using a ruler make sure that the lengths of the potato are all equal. > The purpose for the three pieces is that the experiment can be repeated three times using the same size of potato from the same potato to avoid variations. > Measure 15cm� of hydrogen peroxide using a measuring cylinder. Check the measurement from eye level, while the cylinder is placed on the table. > Pour the hydrogen peroxide solution into the boiling tube carefully. > Take a piece of one of the long length of potato and put it into the solution. > As soon as the potato is placed into the solution, close the boiling tube with the cork immediately and start the timer. > Record the volume of oxygen given off starting at 0 seconds and every 20 seconds for 3 minutes > When you have recorded the measurements, take the cork out of the boiling tube, and pour the solution into the sink and throw the potato, as it is no longer needed. > Wash the boiling tube, so that is it clear enough to pour another 15cm� of hydrogen peroxide. > Once you have cleaned the boiling tube, reset the gas syringe to zero. > Measure another 15cm� of hydrogen peroxide, and repeat the whole experiment twice again using the same sized potato. > Repeat the experiment but varying the surface area by cutting it into halves, the quarters; then into eights and finally to 16 pieces by using a knife and measuring the length using a ruler. ...read more.


Using the knife and measuring the size with the ruler will not always give the accurate answer. This is one of the main factors which cause an inaccuracy on the results table. This factor will lead onto 'overlapping potatoes'. When cutting the potato and putting it into the boiling tube, the potatoes will overlap each other as there is not a lot of space in the boiling tube. Therefore, not all of the surface area is exposed to the hydrogen peroxide solution, causing inaccuracy in the results. Another factor which leads to major errors in the results is the temperature. When there was an increase in the temperature the rate of reaction increase and therefore there was increase in the volume of oxygen given off. When the temperature decreased the rate of reaction slowed down and the volume of oxygen given off became less. Also reading the measurements on the gas syringe would be inaccurate. This is because the readings have the measurements of up to 0.5 cm�. By using a longer and thinner gas syringe, to the nearest 0.2cm�, you can get more accurate answers. Finally, the least important I mentioned is the hydrogen peroxide not covering the potato completely. Not all of the surface area of the potatoes is exposed to the hydrogen peroxide. Accuracy Some of the apparatus I used it measured accurately. One of which is the diameter of the potato. When using a cork borer, for each potato piece the diameter is going to be the same. Also, the measuring cylinder is measured to the nearest 0.2cm� and the gas syringe was to the nearest 0.5cm� Validity of Conclusion If I could do the experiment again, by changing or controlling some of the factors, I can get better results. One of the things I can do is to work out what causes changes in the temperature, and work out a solution which will control that factor. Also, if I had more time I can cut the potato in an accurate length and to the same angle. ...read more.

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