legallyblind
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Hi! My experiment that I'm writing a lab report on turned out to have unexpected results, not supporting my hypothesis. (Context: The experiment's on the effect of pH on enzyme activity, which I deduce through the volume of gas collected, indicating the rate of reaction and thus enzyme efficiency.) I now need to scientifically explain why I got unexpected results for my Conclusion section. (Apart from experimental errors eg reaction time, temperature etc.) I have no idea how! Does anyone know?
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Haviland-Tuf
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What were the unexpected and expected results? And What's the enzyme?
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legallyblind
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(Original post by Haviland-Tuf)
What were the unexpected and expected results? And What's the enzyme?
Enzyme: Catalase (from chicken liver), breaking down h202 to get a mix of o2 and h2 (i just collect them as gas and measure the volume)

I looked up the optimum pH for catalase and it was approx. 7. I tried pHs 5,6,7,8,9 (2 on either side of the literature value) and the order, from largest-smallest volume of gas collected, was ph 6,8,7&9 (same volume), 5. So the optimum pH i got was 6 instead of 7. I also don;t know how to explain the order of the rest, and I've already tried talking about experimental errors.

please save my soul
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Haviland-Tuf
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(Original post by Victoria Soh)
Enzyme: Catalase (from chicken liver), breaking down h202 to get a mix of o2 and h2 (i just collect them as gas and measure the volume)

I looked up the optimum pH for catalase and it was approx. 7. I tried pHs 5,6,7,8,9 (2 on either side of the literature value) and the order, from largest-smallest volume of gas collected, was ph 6,8,7&9 (same volume), 5. So the optimum pH i got was 6 instead of 7. I also don;t know how to explain the order of the rest, and I've already tried talking about experimental errors.

please save my soul
See that is not much of a difference, in fact when I did this experiment a long time ago several students (myself included) got pH 4 as producing the most gas. I put it down to errors and the fact the we used the average to work out the results instead of other measures like the median which actually showed that the difference in the amount of gas being produced is negligible. Obviously only a well-controlled experiment will corroborate the fact that pH 7 is the optimum pH for catalase. For example, you are not studying catalse's optimum pH in vivo you're doing it in a test tube so obviously you will never get that perfect 7 unless you can replicate everything that is happening inside the liver. The biggest issue is the way you're measuring the rate of reaction which can obviously produce so many errors and is not really reliable (but you said you are aware of this.)

One scientific explanation of your results (a stretch in my opinion but nevertheless shows the marker you're using you're brain) is that the liver from which catalase came from was more acidic than basic therefore this would fit in with your results (a healthy liver will be mostly at pH 7 but one that is diseased (acid-base balance disorders)).

You need to just be aware of the fact that your results are not really 'wrong'. At the end of the day your results show that changing the pH affects catalase activity and this is supported by research i.e. if pH is too high or too low enzyme will be denatured and rate of reaction will decrease.
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legallyblind
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thank you so much ) really appreciate the help
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