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Investigate how the surface area of the potato affects the amount of oxygen produced from the reaction: Hydrogen peroxide water + oxygen Potato (Catalyst).

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Planning: The objective of this coursework is to investigate how the surface area of the potato affects the amount of oxygen produced from the reaction: Hydrogen peroxide water + oxygen Introduction: Enzymes are found in every living organism. An enzyme is a biological catalyst which speeds up a chemical reaction in an organism. Catalase is found in the liver but it is also found in potatoes. Catalase is known to be the fastest-reacting enzyme as it has a turnover number of six million. Catalase breaks down poisonous hydrogen peroxide in the liver to make a harmless solution (oxygen + water). This is how an enzyme works: The enzyme can work over and over again; it works rapidly since it isn't destroyed after catalysing the reaction. It is thought that each enzyme molecule has a precise place on its surface, called the active site, to which the substrate molecules become attached. Enzyme + Substrate Enzyme- Enzyme- Enzyme Molecule Substrate Product +Product Complex Complex molecule We can picture the active site of an enzyme molecule as having distinctive configuration into which only certain specific substrate molecules will fit. These diagrams show what happens in the process that takes place in the experiment we will be carrying out. The shape of the active site, and the positions of the different chemical groups within it, ensures that only those substrate molecules with a complementary structure will combine with the enzyme. Thus we have an explanation of the specificity of enzymes, enzyme and substrate fitting together like two bits of a jigsaw puzzle. ...read more.


Firstly, it is important that all experimentation should be carried out in the same environment, in this case the same classroom. This will eliminate any changes in temperature or any other factors which could affect the experiment significantly. Similarly, it is important that all experimentation should be carried out on the same day. It is also very important that all equipment should be washed thoroughly after use; this will ensure that any reactants are washed away. If this was not to happen, the substrate and enzyme could begin to react before the stopwatch is started, rendering the experiment inaccurate. All measurements of substrates and oxygen froth will be taken from eye level to ensure we gain as much accuracy as possible. We will also make sure that the stopwatch is started and stopped as quickly and as accurately as possible. One of the most important features we must stick to is the cutting of the potato. All measurements must be taken with a ruler and using the scalpel the potato cylinder should be cut to the required lengths. Also, any skin left on the potato must be removed to ensure that the full amount of catalase possible is in contact with the substrate. Finally, we will use the same equipment in all experiments, particularly the same potato to ensure there is no room for variation in the concentration of catalase; this will leave no room for inaccuracy in equipment at all. I believe that it is very important to carry out a fair test as the results of the experiment will be the basis for my entire coursework. ...read more.


This could have rendered some of our results inaccurate as either the surface area was decreased as parts of one cylinder were covering parts of another, or that all pieces of potato were not in contact with the solution when the stopwatch was started. In a case such as this, we often repeated the same experiment when we thought it was necessary, and so I believe that not much accuracy was lost here. Although we ensured that every item of equipment was washed in water after use, any residue left on the equipment could render the experiment invalid, also any water left in the measuring cylinder may have decreased the concentration of hydrogen peroxide or contaminated the experiment with chemicals used in water cleansing such as Chlorine. A possible solution to this could have been to use distilled water to wash all equipment with, thus any contamination would have been decreased. Extending the Experiment: If I were to extend the investigation further, I would find it interesting to investigate some of the other variables which affect the decomposition of hydrogen peroxide; some possible extensions are the effect temperature has on and also the PH of the solution. However, both experiments would need to be carried out in a specialist environment as they are both dangerous (hot chemicals) and also the use of acid. I would also find it interesting to compare different catalysts on the decomposition of hydrogen peroxide, such as manganese (IV) oxide or blood which both catalyse the decomposition. I would also choose to use my suggested experiment instead of the one we used in class to see if we are given any different results. Shane Haron ...read more.

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