3. In 2007, we saw the simultaneous release of two articles, in which it was posited that life originated not in seawater as previously thought, but in smaller bodies of water with a K+/Na+ ratio necessary to sustain life. In this conditions sodium pump is not needed and the pump can originate later. But why the pump is needed if K+/Na+ ratio is good? The origin of the sodium pump in conditions where there is no natural need for it may require the agency of Providence.
I have previously thought of the cell membrane as a means to preserve an environment where the replicating molecules survive and thus make them more viable than the molecules alone.
In the above scenario we could have evaporating ponds providing the concentrations, then the cell membranes to protect them, perhaps in a semi-dormant phase, and then the pump.
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Only one question: why membrane sodium pump is needed in the potassium pond? In the pond K+/Na+ ratio is the same as in the living cell.
To contain the concentration when the pond is diluted (rains) and perhaps they get flushed out of the pond into a stream etc. So the proto-life is now capable of surviving drought with the membrane and flood with the pump.
It is surviving to reproduce, it is evolving. I see "life" beginning when evolution begins - beneficial traits are passed down from generation to generation.
Well I was there on a tour so I'm sure we saw the best side of it. I did get a chance to get out and walk around for a bit, and see the parks and canals, as well as the tour high spots.
From my point of view, this means that life has been made possible without the pump. Here are 4 steps of my argument.
Well I do think that the modern cell is the product of billions of years of evolution, so it is a bit difficult to extrapolate back to the first working models. But we can attempt that by breaking it down into steps along the way.
(1) self-replicating molecules arise, many varieties, and they interact and compete for materials, so there is selection of those best able to consistently reproduce their basic pattern.
(3) the semi-permeable membrane allows ions and other atoms or molecules to migrate and balance the inside with the outside environment via openings like ion channels, or what develops into ion channels.
(4) the proto-cell develops the ability to close the ion channel\openings when the outside environment is not compatible with the inside "work environment" and go into a dormant stage or low energy state until the outside environment becomes compatible again.
quote:Nat Rev Mol Cell Biol. Author manuscript; available in PMC 2010 May 1. Published in final edited form as: Nat Rev Mol Cell Biol. 2009 May; 10(5): 344–352. Published online 2009 Apr 2. doi: 10.1038/nrm2668
Two kinds of border guards control the incessant traffic of ions across cell membranes: ion channels and ion pumps. When open, channels let selected ions diffuse rapidly down electrical and concentration gradients, whereas ion pumps labour tirelessly to maintain the gradients, by consuming energy to slowly move ions against them. Because of their diametrically opposed tasks and their divergent speeds, channels and pumps have traditionally been viewed as completely different entities, as alike as chalk and cheese. But new structural and mechanistic information about both classes of these molecular machines challenges this comfortable separation, forcing its reevaluation.
The very different behaviours of ion channels and ion pumps – passive, thermodynamically downhill, and high speed ion movement through channels, versus active, thermodynamically uphill transport, frequent incorporation of enzyme-like reaction mechanisms, and low speed of ion movement through pumps – led to a separation of the efforts to understand them. And only recently have atomic-resolution X-ray crystal structures and high-resolution functional measurements of examples from both classes begun to suggest that ion channels and ion pumps are not as different as once thought and, in fact, have much in common. So now seems an appropriate time to reconsider their similarities and differences ...
One gate versus two gates
The principal difference, in principle, between channels and pumps is that a channel needs no more than a single gate whereas a pump needs at least two gates that should never be open at once. So what is a gate? A gate can be considered to be the part of the protein that precludes ion movement along the translocation pathway in the prohibitive conformation but not in the permissive conformation. ...