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enzymes in cold temperature

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enzymes in cold temperature

Postby biologysucks:( » Wed Dec 05, 2007 5:03 am

what happens to enzymes in cold temperaperature???
i know that it gets denatured if it's too hot, but why don't enzymes work properly in cold??
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Postby MrMistery » Wed Dec 05, 2007 1:15 pm

same reason actually ;)
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Postby canan5000 » Wed Dec 05, 2007 7:39 pm

the cold is not as intuitive as heat. Heat is the abundance in a system and cold is the absence of energy in a system. Hence a thermometer is the an instrument that measures the average kinetic energy of its surroundings. Why do enzymes not work as well in the cold it is because the energy of the system is decreasing causing the molecules to "slow down" there by slowing the diffusion in a system. The enzymes normal substrate is not diffusing a quickly as it would in a heated system, raising the enzymes Km ( affinity for its substrate ). For more info on the effect of molecules in a cold system check out: Enyzmes relative Km in cold temperature enviroments, and Bose-Einstein condensation.
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Postby biologysucks:( » Wed Dec 05, 2007 10:51 pm

omg thank you so much for such a detailed answer :) that really helps!
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Postby MrMistery » Thu Dec 06, 2007 3:06 pm

remember from your chemistry class: the number of productive collisions depends on the temperature of the solution. Lower temperature, fewer collisions. It's the same when an enzyme is present.
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Postby mith » Thu Dec 06, 2007 3:25 pm

cold slowing down molecular collision cannot be attributed to enzyme.
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Postby canan5000 » Thu Dec 06, 2007 5:13 pm

it plays a major for example the perfect enzyme carbonic anhydrase (converts water and carbon dioxide to carbonic acid) the only thing that slows this enzyme down is the rate of diffusion, its turnover number (Kcat) is about 600,000 molecules of product per second. The other perfect enzyme Triose Phosphate Isomerase ( converts DHAP to G3P to avoid a harmful intermediate) that is crucial in glycolsis is also only slowed down by the rate of diffusion (Kcat of about 3000 molecules of product per second). There are other factors like sequential binding and the enzymes affinity for its substrate (Km), but for all general purposes the enzyme cannot function without its substrate and that action is dependent on how fast it comes in contact with said substrate. How fast it converts and moves on to another substrate is another lesson entirely that I do not have space to describe.
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Postby mith » Thu Dec 06, 2007 5:37 pm

The question was, what happens to enzyme in cold, not what happens to reaction rate.
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Postby canan5000 » Thu Dec 06, 2007 6:16 pm

exactly the cold effects the reaction rate by slowing down diffusion of substrate. the question was "why don't enzymes work properly in cold??" This is why enzymatic activity is decreased which is analogous to enzymes not working properly in cold. Its not that they don't work properly but that they don't work as efficiently.
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