For a thing, I am trying to make a detailed model for fluorine based life, starting with the cell. As an alternative to ATP energy, I have chosen the reaction CH4+(4)F2 ==> CF4+(4)HF, I just can't figure out how a cell could produce the methane, as the normal methods I found wouldn't work as carbon and hydrogen immediately react with fluorine so they couldn't ever make methane. Any ways that a cell could make this methane? Additional Information: These cells would use HF as their solvent, assuming that fluorine is also present in the cell. The air composition I have so far is a mix of Fluorine, Nitrogen, Oxygen, and CF4, so those gases would assumingly also be present in the cell. If it helps, add any other gas into the air composition.

  • $\begingroup$ Welcome KaffeeByte. Please take our tour and refer to the help center for guidance. Enjoy the site. $\endgroup$ May 11, 2022 at 1:18
  • $\begingroup$ Thank you very much for pointing that out, I accidently wrote the same half of the equation twice $\endgroup$
    – KaffeeByte
    May 11, 2022 at 1:20
  • $\begingroup$ Not a chemist, but I doubt that Fluorine and Oxygen could coexist in significant quantities $\endgroup$
    – nzaman
    May 11, 2022 at 3:54
  • $\begingroup$ Some background reading: worldbuilding.stackexchange.com/questions/80623/… $\endgroup$
    – Willk
    May 11, 2022 at 16:19

4 Answers 4


Not going to happen out side of magic

Florine and methane as an ATP replacement? Not going to happen. The energy delta the Kcal/mol is far too high for general cellular operations. Like trying to to pay for candy with Kilograms of gold, keep the change.

Fluorine as alternative to oxygen for basic respiratory process. Very unlikely to happen. Again the energy per reaction is just far too high. Methane+fluorine is explosive. The more energetic reactions that exist in known biology need to be handled in steps else the energy jumps will rip apart the cell's machinery.

Biology uses equilibriums

Biology tends to operate almost exclusively with compounds that have equilibrium points at the temperature and pressure that the biological system operates at.

Florine has high chemical potential energy

Florine is very energetic. It will oxidize oxygen compounds. Florine reacts very readily with water. This means no water as solvent. Which implies unknown biology or magic. As mentioned above, methane+fluorine is explosive. Which means that even if the cell is successful in synthesizing methane, within a short time frame the methane will react with the fluorine and no more methane.


Very implausible. The only way that this is remotely possible is if you just declare this is the way my universe works, and carry on.

  • $\begingroup$ I agree, it wouldn't work for Earth-like life. Makes me wonder if there might be some kind of high temperature life that's discovered a way of prizing oxygen and fluorine apart in a reversible reaction - it doesn't strike me as probable, but no expert here. $\endgroup$ May 12, 2022 at 0:24

You don't make the methane. You burn it.

You are making energy. You are burning CH4 with F. There are plenty of organisms that oxidize methane for energy: marvel at the awesome and ancient methanotrophs!

The methanotrophs do not make methane, only to then burn it. Pointless. They find the methane then burn it. So too your fluorine breathers. There is ambient methane they capture and oxidize with the F2 as you have laid out. They too are methanotrophs.

-- This sets aside the environment they live it, which contains fluorine gas to breathe and also methane to oxidize. Why doesn't the ambient fluorine gas just oxidize the methane? How can they coexist? And in our world how can oxygen and methane coexist? The answer to the second from our world could be the answer to the first in yours. Learn the secret ways of the methanotrophs!

Good luck with the fluorine world. I look forward to reading more about it!

  • 2
    $\begingroup$ “The methanotrophs do not make methane, only to then burn it. Pointless.” Plants would like a word. (They make glucose and then later get energy from it) $\endgroup$
    – Topcode
    May 11, 2022 at 11:48
  • $\begingroup$ Even if methane gas was present in the atmosphere of this plant, we come back to our original problem, they would eventually run out of methane, since there is nothing renewing/replacing the methane supply. There has to be some form of life that makes new methane. $\endgroup$
    – KaffeeByte
    May 11, 2022 at 12:00
  • $\begingroup$ @Topcode: you are right. If this is going to be stable over the long term somewhere there are autotrophs who pry the fluorine off the CF4 and regenerate methane. That is not a reaction earth biology can do which is why fluorocarbons persist forever. Or maybe it is not stable and eventually there will be a crash when the methane runs out and there is only CF4. $\endgroup$
    – Willk
    May 11, 2022 at 16:00
  • $\begingroup$ Also I am pretty sure flourine just reacts with methane, with no extra heat needed like with oxygen. So methane couldn't even exist in the atmosphere. $\endgroup$
    – KaffeeByte
    May 11, 2022 at 18:07
  • $\begingroup$ @KaffeeByte Your creatures will need to exist at an interface like the methanogens do - an interface between an environment where F2 is generated (probably some very life unfriendly environment) and a more life friendly environment where they can get methane. And you must remember there is no flour allowed in the fluorine. $\endgroup$
    – Willk
    May 11, 2022 at 19:03

How could hypothetical Fluoride-based cells synthesize methane?

They wouldn't. There's no good reason for it.

For a thing, I am trying to make a detailed model for fluorine based life, starting with the cell. As an alternative to ATP energy, I have chosen the reaction CH4+(4)F2 ==> CF4+(4)HF, I just can't figure out how a cell could produce the methane, as the normal methods I found wouldn't work as carbon and hydrogen immediately react with fluorine so they couldn't ever make methane.

So... why did you choose that reaction for an ATP replacement? It's way too complicated. For something that can function like ATP, you want an easily-reversible decomposition or conformation change reaction, ideally involving a single bond, of a molecule that is easy to grab on to and move around. It won't involve your oxidizer, because it needs to operate in life that hasn't developed aerobic respiration yet! Reacting methane with fluorine doesn't tick any of the boxes.

You won't want to pick out an alternative for ATP until you've got a lot of other stuff figured out, so that you know what building blocks you have to play with. However, something more plausible might be, e.g., a pyridine ring (or a halogenated pyridine ring) joined to a hexafluorophosphate ion chain, which can be cleaved by reaction with HF, or reconstituted to release HF, in an exact analog for the construction and decomposition of oxyphosphate chains joined to adenosine in the ATP/ADP cycle.

But let's back up a little further.

You've got organisms using HF for their biosolvent, presumably on a cold planet with HF seas--something like Niflheim from H. Beam Piper's Uller Uprising. You've got oxygen and carbon in the air, so there's probably a bunch of CF3OF, COF2, and CF2(OF)2 dissolved in the oceans and in the geological environment as sources of structural carbon and oxygen for early organisms, in addition to atmospheric CF4--and there was probably a good bit of primordial NF3 around as well, although aerobic life probably broke it all down to release free nitrogen, which will only react with atmospheric F2 very slowly, just like our own denitrifying bacteria do. You've probably also got primordial or geologically-produced complex fluorocarbons--good material for making early cell membranes out of.

So, aside from lipid analogs, what kinds of macromolecules are your primitive cells going to be made of, and how can it build them out of those primordial components? What extra stuff needs to be supplied, what's left over as waste, and how is that waste managed? What is stable and available in HF solution? For example, early photosynthesizers on Earth needed hydrogen to combine with CO2 to produce sugars and hydrocarbons, but they didn't get it from water, because water is hard to split (and HF is harder!)--they got it from hydrogen sulfide, and produced solid sulfur crystals and extra water as waste. Maybe early photosynthesizers on your world have to use water as a hydrogen source, like ours used hydrogen sulfide, releasing oxygen right away; that would explain the oxygen in the atmosphere. But then again, maybe they actually need excess fluorine, and photosynthesis require jumping straight to cleaving HF... but ending up with excess hydrogen, not fluorine that can start filling the atmosphere!

At some point, life will use up all of the convenient primordial materials, and will have to start fixing its own carbon from atmospheric sources, which basically means conquering the enormous energy hill of cleaving C-F bonds in CF4. That's when you'll start to have excess fluorine that can build up in the atmosphere. But that's not a remotely easy thing to do, and all of the fundamental systems for your fluoride-based life--how membranes work, how catalysts / protein-equivalents work, what the genetic molecule is, what the common substrates are, what the common energy storage structures are, and yes, what stands in for ATP for intracellular energy transfer--will have been settled long before then, and won't rely on the easy availability of free F2.


Fluorine is extremely rare for being where it is in the periodic table (carbon, oxygen, and neon are extremely common, and nitrogen is simply common)... unlike carbon, nitrogen, oxygen, and neon it forms only one stable isotope. It is also fiendishly difficult to extract from minerals due to its strong bonds with just about anything that it ever combines with. Fluorocarbon plastics would be excellent materials for the structure of living things, except that these materials would require synthesis that biological processes cannot do. So we are stuck with calcium carbonate for bone shell, and teeth.

Liquid and gaseous fluorides generally attack water, and fluorocarbons would be difficult to recycle; contrast carbohydrates part of the necessary Calvin cycle in both photosynthesis and respiration.

And then, fluorine itself is one of the nastiest substances that you can imagine.


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