So I accidentally posted this in the wrong thread, (I’m new!)…
I looked this up online to no avail. Why did evolution favor adenosine triphosphate as the prominent energy currency of the cell, and not guanosine, thiamine, or cytidine triphosphate?
Why not?
Evolution does not strive for some sort of engineering perfection. It is a series of jury rigged accommodations working of the previous Rube Goldbergian accommodation.
I agree with DrFidelius in spirit, however there may be some selective pressure, since the molecules are obviously not equivalent. It is also important to note that GTP and CTP play roles similar to ATP as energy transporters, just in different reactions.
adenose is a nice shape.
I notice that a transferase would move the NH3+ from one molecule to another. It may well be more efficient with adenose because it has only one NH3+ site.
This matches up with the nice (symetric, regular, yet simple ) shape of chlorophyll family pyrole-Mg+ structure ??
It stands to reason that actual cell machines are more efficient if made with the similar (in this case , adenose) group in most molecules… the more simple and the more similarity from component to component the better ?
Consider using your alterative xTP’s in the antenna of a chloroblast ? Is it as efficient to build the antenna from very different structure molecules ? does the larger - doubled - molecule want to travel into the required place ?
There is an earth worm that transfers the NH3+ to a completely different molecule - limbrocine. Did it evolve from that point ? It doesn’t seem it can find a more efficient cycle based on limbrocine. It works to store energy, it just creates it and then when needed, uses it. Not much benefit over ATP, ADP, AMP … AxP in the citric acid cycle…
If an alternate xTP cycle was to exist , then what if at some steps ATP was more efficient ? Then ATP would be favoured and it would all switch back ?
pretty much you can research the alternative xTP’s and find why each one has a specific function… eg the next step makes use of the difference in the xTP… But thats a branch off the cycle, not a step on the energy cycle, which is neccessarily going to favour the most efficient…
Cells have the ability to synthesize all four, as needed for DNA synthesis. So, the basic building blocks are available to be used for other purposes.
I looked around on the wiki site for Nucleoside triphosphates and it appears that, at least, GTP is sometimes used for “energy-coupling in a similar manner” - i.e. as energy currency to drive otherwise unfavorable reactions like ATP’s more well-known use.
Given that the pieces are readily available for all four options and have to be for DNA, I’m suspicious that some aspect of the total cycle is slightly more efficient for ATP than for the others, and that was why it won out competitively in most cases (though the GTP mention above seems to indicate it’s not absolute.)
It wouldn’t surprise me that other nucleic acid based energy transferers are “used” on a small scale compared to ATP because there are a lot of reactions that are available to occur within the body, but the protein catalysts that our genes code for are designed to help move along those that are most useful to life. I assume that we’re quite genetically engineered to make use of ATP, but so long as the components of a similar system exist in the cellular fluid, as indeed they must to be able to synthesize DNA, a few stray molecules probably get produced. I can’t say anything more about the potential rate of these reactions, but from what I understand of chemistry and biology the reactions almost surely occur on a very small level.
Of course “used” here implies there there is some sort of thought process that has some sort of end goal for these reactions, but in reality it’s just chemistry occurring somewhat randomly and the body having been evolved to make the best use of what the chemistry automatically provides, along with the catalysts to speed up the ones it really wants to happen. The GTP will transfer the energy without the body really “intending” for it to be done in terms of having specific genes designed to harness it, but it doesn’t hurt anything and helps a little, so there’s no point in actively trying to stop it.
As has been noted, there are GTPases in the body that use GTP in much the same way ATP is used for certain reactions, and CTP and TTP are of course also floating around and used for nucleic acid biosynthesis (they’re the raw materials for making DNA). I don’t think I’ve heard any real speculation as to why ATP may be any better than the others, and it could very well be that it’s not, and that this is one of the many “frozen accidents” of biochemistry that are a result of the slapdash process of evolution - once an ATPase comes along, it’s easier to use that than it is to go back and invent a CTPase.
Lacking any hard data, lsilder’s response is as good as any I’ve ever seen.