Re: MFW journal club - lifting weights makes you thin, cures diabetes?

Tom Anderson wrote:

On Thu, 7 Feb 2008, Andrzej Rosa wrote:

Tom Anderson wrote:

On Thu, 7 Feb 2008, Andrzej Rosa wrote:

Tom Anderson wrote:

[lotsa (unnecessarily) complicated stuff]

Just a comment. You rather didn't need going through all the cycle.
There is a rule that no matter how you go from A to B, the overall
energy remains the same (under constant pressure), so there was a
simpler way to calculate all of that. Normal combustion would work
blimey.

No. That only works if the process is near equilibrium.

Which means, that there should be enough time for changes of temperature
to not result in changes of pressure. It works like that by default in
condensed phase.

Or do you mean, that a cell can't be considered a closed system? For fast
reactions it shouldn't matter, and in bulk of muscle mass it shouldn't
matter at all.

These reactions
happen very far from equilibrium. If you work out the energy liberated by
the oxidation of half a glucose, and the energy required to phosphorylate
however many ADPs to ATP, you'll find the former is a lot more than the
latter.

Here you are probably right. I was thinking like a chemist, which means
that for me heat is heat, no matter if you have useful fuel out of it, which
can be converted into mechanical energy, or just a byproduct heat, which
needs to be sweated out.

For this process, the amount of energy 'lost' to entropy (really,
the amount of energy given up to drive the reactions forward quickly)
is fixed by the stoichiometries of the enzymes, which is what i looked at.
Except i didn't account for the 'clutch slip' by leakage of protons across
the mitochondrial membrane, which can be a significant amount.

I managed to never learn biochemistry on this level (which wasn't all that
easy), so I can't comment here. (But your wording regarding entropy, energy
and kinetics makes me cringe a bit. ;-))

[...]
None the less, I found other sources where they claimed, that oxygen
cost of producing energy from fat is higher, so I repeated a wrong
statement without checking. Now I feel ashamed, as I should!

This would be a very quiet group if we never did that.

And there is no police here to stop us from trying (unlike on various
forums).

I think it's more likely that the PKB activation was making the mice waste
more energy as heat.

Or something. Didn't they measure respiratory exchange rate? This is
used to find the primary source of fuel for real, not just in popular
press.

Not that i noticed.

Well, that's how it's supposedly done. Indirect calorimetry, or something
like that. You measure the amount of exhaled CO2 in comparison with used
O2 and work out the relative amount of carbs and fats used out of required
percentages for stoichiometry to work.

[...]
--
Andrzej Rosa
.

Relevant Pages

  • Re: College project : Is the number of human chromosomes fixed, or
    ... even considering the universe as ... in essence, if you have a blob of matter, ... of energy is coincident with an increase ... a definition for 'heat' which is based ...
    (talk.origins)
  • Re: College project :
    ... even considering the universe as ... in essence, if you have a blob of matter, ... of energy is coincident with an increase ... a definition for 'heat' which is based ...
    (talk.origins)
  • Re: electricity from heat
    ... | As we know that generation of electric energy from heat energy is ... The easiest way to increase the amount is the one we use. ... Burn coal or oil, create steam from water, use that to rotate a turbine ... Same with heat, ...
    (sci.physics)
  • Re: liquid nitrogen
    ... If just a small amount of heat is added, ... Where does the energy come from? ... yet the explosions are much the same. ...
    (sci.physics)
  • Re: E = mc^2
    ... >> The amount of energy arriving at a surface is equal to the amount ... conduction or convection to carry off an equivalent amount of heat. ... A simple energy balance. ... Angular momentum does not have to be ...
    (sci.physics.relativity)