Writing repot, need some desperate insight

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madman1611
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Writing repot, need some desperate insight

Post by madman1611 » Wed Dec 19, 2007 2:19 am

Hey, guys. I recently conducted a lab on the an industrial catalyst (manganese dioxide) vs. the catalase enzyme and their effectiveness upon hydrogen peroxide under external factors (pH and temperature). For the temperature part, I'm able to explain why, but for pH I have no idea as to why the catalytic activity of the (according to results) manganese dioxide was inhibited with the addition of basic and acidic pH buffers.

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mith
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Post by mith » Wed Dec 19, 2007 2:31 am

Did the catalyst react with the acid/base?

Did you measure the pH after adding the catalyst?

Review the mechanisms of manganese dioxide, does excess proton/hydroxide ions inhibit it?
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madman1611
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Post by madman1611 » Wed Dec 19, 2007 5:10 am

Hey, Mith. Thanks for the reply. My primary problem with this lab is I didn't think it well through the initial stages of devising the experiment. See, the catalase enzyme and its decomposition of hydrogen peroxide I understand, but I have no clue as to how the manganese dioxide catalyzes the decomposition. e.g. like if it contains an active site to which the hydrogen peroxide molecules will bind. sorry if this is really noobish, but bio really isnt one of my stronger subjects

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Post by blcr11 » Wed Dec 19, 2007 6:42 pm

I don’t know that the mechanisms are all that different between catalase and MnO2, The chemistry of catalase (which, by the way, would be a solid if it weren’t dissolved in water or some sort of buffer) is an iron-catalyzed redox reaction with hydrogen peroxide. MnO2 is not an enzyme, but it is a solid-phase catalyst. Oxygen-18 labelling studies have shown that the oxygen released comes completely from the peroxide for both of these reactions; none at all from solvent or catalyst, which is why I say the mechanisms are likely to be similar. Changing the pH of a catalase solution most likely changes the charge and possibly the overall shape of the catalase molecule; in the extreme even denaturing the enzyme and/or expelling the iron. Changing the pH of a suspension of MnO2/H2O2 solution most likely removes some of the catalyst by chemical reactions converting the Mn(IV) to other oxidation states that are less or non-reactive toward H2O2.

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