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Denatured Enzymes in Potatoes

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Enzymes: Coursework The first investigation we carried out was looking at what happens to different concentrations of yeast. Method. We found that we should investigate enzymes more. Our Second Investigation looked at the affect of yeast when applied to different temperatures. Method. We found it was hard to use that method because of the gas expansion. Yeast has a surface area that is hard to control, and it would be better to use something else that we could control more easily. To find out what would be best to use we narrowed down our choices to liver and potato. We then carried out an investigation to decide which would be more suitable. We took a potato, cut it into two equal chips and placed it into separate conical flasks. We then took a piece of liver, cut it into two equal liver slices and placed them both into separate conical flasks. We placed one conical flask with potato and one conical flask with liver, into a water bath. We placed an unturned measuring cylinder, full of water, into a bucket also full of water and fed a tube with a bung at the end, up the measuring cylinder. We added 50ml hydrogen peroxide to flask holding the cold potato and put the bung in the top. Bubbles of Oxygen were forced up the cylinder, after two minutes we measured it and applied the same process to the cold liver. ...read more.


This will prevent as much gas release and will leave a smaller chance of anything affecting our final results. The method, which I used, is reliable and can be counted on to give accurate results. There are no evident random errors, errors that have aroused by fault or any systematic errors, because of fault with the apparatus. To improve my experiment, I could have paid more attention in controlling the variables. I have confidence in my results because they are close together and constant, also my line of best fit makes a smooth curve through the majority of my results, making them reliable. I think my results were accurate enough for the task and they showed the optimum temperature that catalyses works at, which is 40�C. There was one constant anomalous result in my results, which was for the temperature of 35�C. It was very clear that it was an anomalous result because it lay quite far apart from the other results in the graph. This is most likely to be there because the water baths were at the wrong temperature or the amount of gas in the gas syringe was not read properly. The line of best fit on the graph of results shows a positive correlation up to 40�C and then a sudden negative correlation with a steep gradient. This is because, as the temperature rises, the activity of the enzyme increases as the atoms within the enzyme begin to vibrate more vigorously, but at 40�C ...read more.


This hypothesis can be affected by temperature and pH because if the enzyme becomes denatured by either a temperature that is too high, or if the pH is to acidic or alkali and the active site becomes the wrong shape for the specific substrate molecule to fit. Enzymes can be used over and over again though as long as they do not become denatured. Particle Theory: The Particle Theory states that the rate of reaction depends on how often and how hard the reacting particles collide with each other. That the particles have to collide with each other to react, and they have to collide hard enough. So more collisions increases the rate of reaction This is relevant for the temperature affecting the activity of an enzyme because when the temperature is increased the particles all move quicker. If they're moving quicker, they're going to have more collisions. For this investigation it means that when the temperature is increased the hydrogen peroxide molecules and the catalyse molecules move quicker, so there will be more collisions of the hydrogen peroxide with the active site of the catalyse, increasing the rate of reaction, until the catalyse becomes denatured. This is relevant for the surface area affecting the activity of an enzyme because if one of the reactants is a solid, in this investigation, the potato, which is the source of catalyse, breaking it up into smaller pieces, will increase its surface. This means the particles around it in the solution, hydrogen peroxide, will have more area to work on so there'll be more collisions between the two particles. ...read more.

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Response to the question

This piece of coursework superbly explores the effect on enzymes due to temperature, although towards the beginning they seem to waste time deciding on liver or potato samples. In my opinion, it should be apparent that the size of potato ...

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Response to the question

This piece of coursework superbly explores the effect on enzymes due to temperature, although towards the beginning they seem to waste time deciding on liver or potato samples. In my opinion, it should be apparent that the size of potato samples are easier to control, and this part of the experiment doesn't show off any skills. However, don't be put off by the introduction, as when the essay begins to discuss the effect of temperature it has some strong analysis.

Level of analysis

The analysis in this piece of coursework is very strong. I liked how they clearly displayed a table of the variables which needed to be controlled, why this could affect the experiment, and how this would be kept constant. This shows a clear understanding of the importance of fair tests when conducting experiments, and this would be looked upon well in any piece of scientific coursework. Another strong point was the awareness that even though 45 degrees showed the highest result, this may not be the optimum. In my experience, showing this sort of skill, then going further to prompt the need for more results between a certain range, will gain credit. It is nice to see a hand-drawn graph which has been scanned in, and it is a good evaluative point to identify known anomalies. The explanation of the lock-and-key hypothesis, collision theory and denaturing are all areas which show full understanding. Whenever talking about denaturing, I would always make sure to note that the change of shape in the active site is irreversible. This piece of coursework hasn't made clear that when the temperature decreases (having been high enough to denature) the enzyme will no longer function.

Quality of writing

This essay is structured well and uses scientific terms throughout. At times, the language is not as assertive as it could be. For example they say "I think I have enough evidence to draw a conclusion". If the candidate had said "There is clearly enough evidence to now draw a conclusion" it sounds much more sophisticated. Note how I have not used the first person - although it is not overly frequent, trying not to use the first person in essays will prepare you for A-Level and beyond!

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Reviewed by groat 11/02/2012

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