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Topic: how to interpert cross htaching grap  (Read 2545 times)

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Offline sinister18

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how to interpert cross htaching grap
« on: August 29, 2012, 09:52:58 AM »
hey

can someone please explain me how to interpert the following graph and cross hatched graph in general?

http://imageshack.us/photo/my-images/255/35299305.jpg/
« Last Edit: August 29, 2012, 11:46:37 AM by Arkcon »

Offline Babcock_Hall

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Re: how to interpert cross htaching grap
« Reply #1 on: August 29, 2012, 08:16:52 PM »
What is your interpretation?  You have to show an attempt, according to the rules of this forum.

Offline Babcock_Hall

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Re: how to interpert cross htaching grap
« Reply #2 on: August 30, 2012, 09:11:22 AM »
I have never seen cross-hatching used in this kind of graph before (so take this with a grain of salt).  However, the basic concepts are more familiar.  Let us think of the solid black line as being composed of two halves, a left leg and a right leg.  The solid black line is the rate or activity of the enzyme on a percent scale.  The enzyme has (at least) two forms, EH and E-, with an equilibrium governed by pKa1.  At high pH most of the enzyme is in the E- form, but at pH values below pKa1, the enzyme is mostly in the EH form.  I think that E- is prevalent in the hatched area to the right of the left leg.  The substrate also has two forms, SH+ and S, and this equilibrium is governed by pKa2.  At pH values below pKa2, most of the substrate is in the SH+ form, and this corresponds to the hatched area on the left side of the right leg.  Beyond that pH, S would be the predominant form.  The cross-hatched area is a region in which both E- and SH+ can be found, and the model implicitly assumes that these two ionic forms are the only pair that is catalytically active.  Therefore, this is where the rate (activity) is highest.

Offline Babcock_Hall

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Re: how to interpert cross htaching grap
« Reply #3 on: August 31, 2012, 09:05:30 AM »
Can you write the mathematical equations that define Ka1 and Ka2 or the acid dissociation (chemical equilibrium) reactions that are governed by Ka1 and Ka2?  This might help you see what is going on.

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