Thermodynamic problems (Pentcho Valev)

Lukasz Salwinski lukasz at wlheye.jsei.ucla.edu
Tue Oct 21 21:56:28 EST 1997


>give a concrete answer to any question. Instead, you prefer to hint at my
>ignorance - on this forum and in private messages. That's OK - I am rather

not really. I'm saying what's wrong and give poiners to references. In private
I've just asked what's your formal education. I don't think it's insinuation
of any kind. Just curiosity.


>possible, in concrete numbers. So let me repeat the questions - please try
>to answer them - only then can the duscussion be fruitful.

>1, 2, 3

check any electrophysiology textbook eg. 
   B. Hille, Ionic Channels of Excitable Membranes


another review and pointers (refereces to papers by Cafiso and Flewelling) to partitioning 
based methods (no need for those pesky electrodes):
   Honig, Hubbel, Flewelling, Ann. Rev. Bioph. Bioph. Chem. 15:163 (1986)

or search for papers by Cafiso & Hubbel form late '70, early '80

> 4. As the test charge comes from infinity and enters the right end of the
>system, what does it meet: a) nonzero charge density b) nonzero field
>c) nonzero concentration of some ion d) a combination of some of these


as already stated before - d


>5. What if the initial KCl concentration in the left-hand compartment is
>10 mM whereas that in the right-hand compartment is zero? Please try to
>describe how the charge density, the field and the potential change
>from the membrane to the right, up to infinity. (The potential in the
>right-hand compartment cannot be measured since the phase is non-conductive,
>but calculations based on thermodynamics show that the potential goes to
>infinity with distance. Would you agree?)

nope. can be measured, do not go to infinity. hint: some of K ions cross the
membrane and generate transmembrane potential. value depends on the ratio of
the compartments

>6. If the ATP-ADP-P system does  50 KJ/mole work, you should be able to
>show the origin of this energy, if you believe in the first law. So please

there's no trust involved. energy conservation (aka the first law) was 
demonstrated quite a few times. dG (I guess that what you are asking about) has 
actually more to do with the second law.

>do this - 50 KJ work is done of which 20 KJ are the internal energy (enthalpy).
>Where does the rest (30 KJ) come from?

entropic term 

references: any physical chemistry textbook eg Atkins, Physical Chemistry


>Of course I do have someting to say about these things, but would like to
>know your concrete answers. 

concrete answers are in the above books/papers. I've got no time/will to play
a teacher here. Do your reading.


lukasz




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