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Origin of Life: Hypothesis Traces First Protocells Back to Emergence of Cell Membrane


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#1
MelT

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Dec. 20, 2012 — A coherent pathway -- which starts from no more than rocks, water and carbon dioxide and leads to the emergence of the strange bio-energetic properties of living cells -- has been traced for the first time in a major hypothesis paper in Cell this week.


At the origin of life the first protocells must have needed a vast amount of energy to drive their metabolism and replication, as enzymes that catalyse very specific reactions were yet to evolve. Most energy flux must have simply dissipated without use.
So where did it all that energy come from on the early Earth, and how did it get focused into driving the organic chemistry required for life?
The answer lies in the chemistry of deep-sea hydrothermal vents. In their paper Nick Lane (UCL, Genetics, Evolution and Environment) and Bill Martin (University of Dusseldorf) address the question of where all this energy came from -- and why all life as we know it conserves energy in the peculiar form of ion gradients across membranes.
"Life is, in effect, a side-reaction of an energy-harnessing reaction. Living organisms require vast amounts of energy to go on living," said Nick Lane.
Humans consume more than a kilogram (more than 700 litres) of oxygen every day, exhaling it as carbon dioxide. The simplest cells, growing from the reaction of hydrogen with carbon dioxide, produce about 40 times as much waste product from their respiration as organic carbon (by mass). In all these cases, the energy derived from respiration is stored in the form of ion gradients over membranes.
This strange trait is as universal to life as the genetic code itself. Lane and Martin show that bacteria capable of growing on no more than hydrogen and carbon dioxide are remarkably similar in the details of their carbon and energy metabolism to the far-from-equilibrium chemistry occurring in a particular type of deep-sea hydrothermal vent, known as alkaline hydrothermal vents.
Based on measured values, they calculate that natural proton gradients, acting across thin semi-conducting iron-sulfur mineral walls, could have driven the assimilation of organic carbon, giving rise to protocells within the microporous labyrinth of these vents.
They go on to demonstrate that such protocells are limited by their own permeability, which ultimately forced them to transduce natural proton gradients into biochemical sodium gradients, at no net energetic cost, using a simple Na+/H+ transporter. Their hypothesis predicts a core set of proteins required for early energy conservation, and explains the puzzling promiscuity of respiratory proteins for both protons and sodium ions.
These considerations could also explain the deep divergence between bacteria and archaea (single celled microorganisms) . For the first time, says Lane, "It is possible to trace a coherent pathway leading from no more than rocks, water and carbon dioxide to the strange bioenergetic properties of all cells living today."

#2
yurigadaisukida

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I wonder if there is life on Neptune

#3
MelT

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I wonder if there is life on Neptune


Personally I'd say there is a good chance of life in most circumstances.

MelT

#4
MysteryRoach69

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It must have been between these protocells and when Adam and Eve existed that god decided to intelligently design all life, using themes of body design of course. Thats why lots of animals have four limbs and similar facial designs :D

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Rotawee

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#6
Timesplasher

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Hello Melt. Is this the only known environment that this type of "stuff" has been found to occur in.

deep-sea hydrothermal vents ?

I am being serious :smoking:

#7
MelT

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Hello Melt. Is this the only known environment that this type of "stuff" has been found to occur in.

deep-sea hydrothermal vents ?

I am being serious :smoking:


It depends what you mean to be honest. Hydrothermal vents are a perfect environment for it to happen, but there are bound to be other circumstances where similar interactions take place.

MelT

#8
Timesplasher

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It depends what you mean to be honest. Hydrothermal vents are a perfect environment for it to happen, but there are bound to be other circumstances where similar interactions take place.

MelT


I get confused when I think of one off potential evolutions I want to know why they cease to evolve - all the ingredients are there for it to still take place.

I suppose the time taken to view it occurring maybe a factor. :(

Edited by Timesplasher, 30 December 2012 - 12:32 PM.


#9
Timesplasher

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Have the scientist in the article provided a example of what the discovered
"living cell/s" consist of?

or is it just a hypothesis based on the potential production of energy required to fuel the growth of an unknown object ?

Both parts of the hypothesis needs to be proven for a true connection to be made.



I also just watched Hawkins about his version of multiple keys to the universe blah blah

so now im wondering if anyone has suggested a similar M theory based on the understanding of what the first:) living cell consists off. Surely the same rules apply.

Whats the current conversion rate from living cell to proton atm?
Is this a fair question?

Edited by Timesplasher, 30 December 2012 - 01:29 PM.


#10
MelT

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I get confused when I think of one off potential evolutions I want to know why they cease to evolve - all the ingredients are there for it to still take place.


The same processes will still be taking place if the conditions that might have formed life are still there. But as you say, this isn't something we can watch happening in real time.

MelT

#11
MelT

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=Timesplasher;16758255]Have the scientist in the article provided a example of what the discovered "living cell/s" consist of? or is it just a hypothesis based on the potential production of energy required to fuel the growth of an unknown object ?

None of the above.:) It's about the fact that all life on earth exists by virtue of a particular kind of 'metabolic' system. This same system can be found in creatures that have evolved and still live around hydro-thermal vents, and we know that they existed on earth long before life arose. This means that life is extremely likely to have formed around them.

'...The simplest cells, growing from the reaction of hydrogen with carbon dioxide, produce about 40 times as much waste product from their respiration as organic carbon (by mass). In all these cases, the energy derived from respiration is stored in the form of ion gradients over membranes.

This strange trait is as universal to life as the genetic code itself. Lane and Martin show that bacteria capable of growing on no more than hydrogen and carbon dioxide are remarkably similar in the details of their carbon and energy metabolism to the far-from-equilibrium chemistry occurring in a particular type of deep-sea hydrothermal vent, known as alkaline hydrothermal vents....'

Both parts of the hypothesis needs to be proven for a true connection to be made.

It isn't a hypothesis, it's a statement that life can be sustained in harsh temperatures and living on nothing other than hydrogen and carbon.

so now im wondering if anyone has suggested a similar M theory based on the understanding of what the first:) living cell consists off.

Sorry?

Surely the same rules apply.

I'm not sure what you mean?

Whats the current conversion rate from living cell to proton atm?

Is this a fair question?

With all due respect, it doesn't have any meaning. Could you say it another way?

MelT

Edited by MelT, 30 December 2012 - 03:26 PM.


#12
Timesplasher

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Im just trying to get in on sum science action :cool:

Edited by Timesplasher, 30 December 2012 - 02:28 PM.


#13
MelT

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Im just trying to get in on sum science action :cool:


Sorry, I understand:)

MelT
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