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Offline Derrick6109

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Need help on a essay
« on: June 17, 2019, 04:25:26 PM »
I have to do a essay and this is what I need to do. I need help finding a way to make a 250 word essay and also understanding this topic more. I understand most of it but, I have honestly no clue how light of entropy and chemical spontaneity is included in chemical evolution. Thank you.

Many evolutionists believe that the large, complex molecules (proteins, DNA, etc.) found in living cells were originally formed as much smaller molecules spontaneously joined via endothermic processes; this presumed process is often called chemical evolution. Evaluate chemical evolution in light of entropy and chemical spontaneity.



Offline jeffmoonchop

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Re: Need help on a essay
« Reply #1 on: June 17, 2019, 05:46:56 PM »
How they've worded that makes it look like you're meant to discuss 'light of entropy' when I think they just mean to discuss how this could happen based off entropy. It could be a discussion about how if you leave two things together for long enough it will randomly react. We know chemicals need energy to react but if you leave a vat of reactants together for a long time, adding no energy to it, some molecules may randomly overcome this energy barrier by overcoming the vast odds against them.

Offline Enthalpy

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Re: Need help on a essay
« Reply #2 on: June 18, 2019, 06:35:47 AM »
I wonder if the enlightenment by entropy and spontaneity will bring much to the topic...

The interrogation is how very complex molecules of life, including DNA for instance, could build from inert matter, without the intervention of a god or similar. We know already that amino acids form spontaneously from "simpler" molecules, but the way from amino acids to living molecules is extremely long.

An attempted answer like "life can happen spontaneously" would involve the huge amount of molecules available on Earth, especially in the Ocean. Then, the formation ΔG of the complex molecule would lead to a proportion of this molecule in the Ocean, and if one (1) such molecule is formed randomly, one might boldly argue that it created life.

So this looks like a scientific answer to the interrogation, and possibly this essay is expected from you, but I have big doubts about how convincing that particular answer is.

ΔS, ΔG etc let compute equilibria only. Maybe sunlight was instrumental in creating life. Or the disequilibrium created by black smokers at the Ocean's bottom. Or thunderbolts. Or radioactivity and cosmic rays. An equilibrium computation can't possibly evaluate this. Unfortunately, we have manageable theories (thermodynamics) only for equilibria.

Equilibria don't tell how long a reaction takes. At nuclear equilibrium, all atoms on Earth would have fused to iron, which obviously isn't the case, so either they lacked time or some conditions aren't met. So equilibrium isn't the whole picture.

And then, we have difficulties with the accuracy.

We know imperfectly one set of molecules involved in life on Earth. Could there be trillions of trillions of other molecules that can live? On Earth, life as we know it pre-empts about all accessible organic material, so we can't see the other options.

Possibly life appeared on meteoroids and seeded the Earth, or it appeared on an other planet offering completely different conditions, and meteoroids transported it, as for instance we have a fragment of Mars fallen on Earth. Figures from Earth wouldn't match at all.

My worst doubt is: how many life molecules are needed, and how strongly organized? Even if chance makes one DNA molecule or some simpler version, it demands an elaborate context to multiply, like enzymes and feedstock at the right time and place, which thermodynamics can't evaluate. Probabilities by DNA's ΔG alone would be completely off.

Finally, entropy is often claimed to represent disorder as opposed to organization and life, but to my understanding, our definition of ΔS based on ΔQ does not. Here we might get fooled by the words and stone-old philosophy. ΔG only tells about energy, not complexity. The simpler definition of ΔS used for chemical equilibrium doesn't distinguish separated D2 and H2 from their mixture because ΔQ=0. If you put the base pairs randomly in DNA, ΔG is the same as in DNA from a living being, so thermodynamics isn't the whole picture. Life isn't especially endothermic, if you consider that aminoacids compose life and they supposedly appeared in an environment of CO2, H2O and N2, rather than the present O2-rich  atmosphere that was created later by bacteria using sunlight.

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