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enzymes and temperature

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enzymes and temperature

Postby karlasa528 » Wed Nov 07, 2007 11:49 pm

im currently in gr 12 and in my bio class, I just learned about enzymes.
a few days ago, my bio class had an enzyme lab.
the lab was about how enzymatic rxn rate varies under different conditions. We used a beef liver(catalase) and hydrogen peroxide.

one of the procedures was putting a piece of liver into an empty test tube, and putting the tube into a boiling water for 5 min, then pouring 10 mL of hydrogen peroxide.
According to what I have learned from a textbook, the boiled liver was not supposed to react with hydrogen peroxide. I learned that optimum temp for catalase (which is in the liver..) is 37 degrees celsius, and high temperature (about 100 degrees celsius in this case) denatures enzymes.

but the piece of boiled liver (i could see that the liver was actually boiled because the colour of the liver was changed after 5 min. in the boiling water) reacted with the 10 ml of hydrogen peroxide quite vigorously.
and it means that catalase in the liver is still working properly, no denaturation due to high temperature. right?

im supposed to suggest in my lab report a reason why this reaction had happened, but i just cant think up of any possibilities even after searching through many internet sites.
my opinion is that maybe 5 min was not enough time for catalase in the liver to denature.. but i dont think it really makes sense :cry:

Please help me with your explanations, or at least your opinions! :D
biology is so hard but still a very interesting subject to study :P
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Postby mith » Thu Nov 08, 2007 1:45 am

Did you cool your test tube before pour the peroxide?

Did you do a control test to gauge the reaction when poured into something that isn't supposed to react such as muscle(steak)?
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Postby blcr11 » Thu Nov 08, 2007 2:48 am

How large a piece of liver was it? If you had a "largish" piece, 5 minutes may not have been enough time to heat the entire sample to 100 C; just like it takes a few hours of baking to heat the center of the chicken to 165 C, the mass of tissue acts like an insulator and slows down the rate of heating. Better to mince the liver into small and uniform size pieces. If you happen to be at higher elevations, I suppose the boiling point of water may also be a little lower than if you were at sea level, but that should only be a few degrees off and probably wouldn't account for much, but it might contribute.
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