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Potato and Catalase Investigation

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Prediction and Scientific Knowledge Potato contains an enzyme called Catalase. This breaks down the hydrogen peroxide, and oxygen and water are released. The more potato added, therefore more catalase, the more oxygen and water are released. This will be true until all the hydrogen peroxide has been broken down. So as more potato discs are added, the reactions will become more violent and more oxygen will be released. The enzyme found in potato is Catalase. This is found in virtually all living tissues. It catalyses the breakdown of Hydrogen Peroxide. This reaction releases oxygen and water because: HYDROGEN PEROXIDE --> WATER + OXYGEN If hydrogen peroxide was left in a beaker or exposed to air, it would take days or weeks even to decompose. By adding the potato, we are speeding up the decomposition process. The best way to explain this is the Lock and Key hypothesis. It is thought that each enzyme has a place somewhere on the molecule called and active site. The reacting chemicals fit into this site and they react with each other momentarily, and the molecule strand is broken. ...read more.


No. Potato Discs Volume of Oxygen (cm�) 1. This experiment has to be a fair test. All measurements of hydrogen peroxide (50cm�) must be the same and lengths of potato discs (4cm) must be the same. 2. This experiment also has to be a safe one so remember to wear goggles at all times. Gloves can also be worn. 3. Gather equipment together and set everything up as shown in diagram. Use the smallest measuring cylinder for the first few results, but as more potato is added, the size of measuring cylinders should progress up. 4. Cut one potato disc to 4 cm long and measure out 50cm� Hydrogen Peroxide into a conical flask. 5. Put the potato into the conical flask and immediately after put the bung in the end and soon after bubbles should come up through the tube in the measuring cylinder. This is the oxygen. 6. Record how much oxygen is in the cylinder by reading off the markings. 7. Repeat steps 4 to 6 adding one more potato disc each time. ...read more.


This second graph has a smoother curve. I worked out that each disc had an area of 17.5929cm�, and I just multiplied this number by the amount of discs added to get the total surface area of all the discs added. Reading back the method, I think it is clear what has to be done. If I had to do this experiment again I wouldn't change anything. This method was reliable, and it will be if you follow the exact instructions. The results I recorded were very accurate, apart from result five. This is an anomalous result shown on both graphs. This was probably due to an inaccurate reading. If I had time I would do this again to get the right result. This experiment has shown that catalase, found in potato, speeds up the breakdown of hydrogen peroxide, and the products of this reaction are oxygen and water. If I had more time for this experiment I would've got more results, done a more investigating into enzymes, particularly catalase, and tried to find a better way of collecting the oxygen to get more accurate results. Investigate the effect the enzyme found in Potato has on Hydrogen Peroxide. ...read more.

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Response to the question

Overall an okay experiment with basic scientific knowledge expected for GCSE employed to create an experiment. The conclusion is adequate as it analyses the results accurately to get a picture of how the experiment went and tries to make ...

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Response to the question

Overall an okay experiment with basic scientific knowledge expected for GCSE employed to create an experiment. The conclusion is adequate as it analyses the results accurately to get a picture of how the experiment went and tries to make some suggestions for improvement. The candidate lacks results in this example.

Level of analysis

The prediction and scientific explanation are correct but the science is quite hard to follow due to the fact that the candidate is not clear in each statement they make about the role of catalase. I was not sure where hydrogen peroxide came in their experiment at first this confuses most of the earlier prediction statements until their equation. Rather than writing the equation out in words to be more accurate this should be written out with correct scientific state symbols and notation. The candidate should explain why they kept certain factors constant to show greater scientific understanding. The candidate does not think of very thorough improvements and this should be done to show an understanding of why the experiment had some anomalous results and how it could have been made better.

Quality of writing

Minor grammatical errors in places. Otherwise, spelling, grammar and punctuation are okay. The candidate does not include their results or the graphs they mention which may make it hard for other readers to follow their experiment as a model for what they should be getting.

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Reviewed by skatealexia 11/07/2012

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