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Author: adonsant Big red star, 1000 posts Old School Fool Add to my Favorite Fools Ignore this person (you won't see their posts anymore) Number: of 25048  
Subject: Re: Poll: First Life Form Date: 12/20/2012 5:04 PM
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Methane and hydrogen sulfide aren't energy rich molecules? You might want to tell the modern-day organisms that rely on these molecules for energy that they're doing it wrong.

You're talking about a sophisticated organism. The subject of this post is the initial life form. Completely different issues.


I don't see why. Available energy is available energy. Do you have any evidence to support your assertion that the initial life form(s) couldn't use protons from hydrogen sulfide?

Could the life have initially used hydrogen sulfide as a proton/energy source? Fortuitously, Cell just published a paper hypothesizing that:

Volume 151, Issue 7, 21 December 2012, Pages 1406–1416

Harnessing energy as ion gradients across membranes is as universal as the genetic code. We leverage new insights into anaerobe metabolism to propose geochemical origins that account for the ubiquity of chemiosmotic coupling, and Na+/H+ transporters in particular. Natural proton gradients acting across thin FeS walls within alkaline hydrothermal vents could drive carbon assimilation, leading to the emergence of protocells within vent pores. Protocell membranes that were initially leaky would eventually become less permeable, forcing cells dependent on natural H+ gradients to pump Na+ ions. Our hypothesis accounts for the Na+/H+ promiscuity of bioenergetic proteins, as well as the deep divergence between bacteria and archaea.

http://www.sciencedirect.com/science/article/pii/S0092867412...

There is a lay summary on Nature's website:

http://www.nature.com/news/how-life-emerged-from-deep-sea-ro...

That's not quite true. Arguably one of the most important processes for modern cells, glucose transport is mediated by diffusion through a passive transporter in the vast majority of cells.

How is that any different than selective diffusion...which is passive. "Transport" would seem to suggest active. Active requires coupled energy.


In Biology "transport" is merely the movement of a molecule accross a membrane. Transport can be active, meaning transport against a concentration gradient (although there are a few cases where active transport is performed in the direction of the gradient to speed up the rate of transport), or passive, where transport is in the direction of the gradient. "Selective diffusion" just means a channel is involved (as opposed to diffusion of the molecule through the lipid membrane, which happens with some hormones).

I'm still wondering how you would have answered your own poll.

-Anthony
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