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I've been working on the anatomy of my boron based life using alternative biochemistry. But I've recently came across a problem that I can't solve on my own. In oxygen breathing life on earth, the macromolecule known as hemoglobin located in the blood is what transports oxygen throughout the body.

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However, my boron based life doesn't breathe oxygen, in fact oxygen is quite dangerous to my species. As it would form strong bonds with the boron which would kill off the life on my planet. Instead, my boron based life breathes methane which is then broken down in their body for the hydrogen. Due to this function in their body, what alternative macromolecule could I use in their blood to transport the hydrogen that doesn't also contain oxygen.

I hope this question is clear enough to answer. If not, let me know in the comments.

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    $\begingroup$ Three ideas from a non-expert. 1) I do not think that all oxygen should be banned from your planet (that might even be impossible, considering that oxygen is quite an abundant element). You only have to have it bonded in molecules and crystals. 2) What is the purpose of methane intake? How do they use it to produce energy without free oxygen? Spitting metane into carbon and hydrogen is endothermic. 3) You can not simply ask for a specific molecule in an alien biochemistry. Their macromolecules are probably built up from totally different component parts (not amino acids) $\endgroup$
    – b.Lorenz
    Aug 13, 2018 at 19:33
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    $\begingroup$ There is something fundamentally wrong in your question. Oxygen is used because, oxidizing molecules, produces energy. Breaking down methane to hydrogen requires to supply energy. $\endgroup$
    – L.Dutch ♦
    Aug 13, 2018 at 19:33
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    $\begingroup$ Could you possibly have the aliens convert the methane to something else prior to transporting it, then convert it back to methane when they're done? In any case, you might be wandering outside the boundaries of what worldbuilders without chemistry degrees are able to answer. Might be a good question for the Chemistry or Biology SE. $\endgroup$
    – boxcartenant
    Aug 13, 2018 at 21:12
  • $\begingroup$ @L.Dutch your dilemma could be solved with some kind of methane photosynthesis. Still a valid point but perhaps solvable. $\endgroup$
    – userLTK
    Aug 14, 2018 at 4:01
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    $\begingroup$ @userLTK, I see no advantage in using energy to break up methane into hydrogen and then oxidize it. At best you get the same net energy you would get directly oxidizing methane (less if you account for actual yields) $\endgroup$
    – L.Dutch ♦
    Aug 14, 2018 at 6:13

2 Answers 2

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Need something to carry hydrogens? Digging boron? How about boron hydrides: boranes.

https://en.wikipedia.org/wiki/Boranes

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Some of these get big. I like the idea of flipping back and forth between the diborane and tetraborane to drop off or acquire hydrogens.

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    $\begingroup$ Those will not reversibly bind hydrogen or methane analogously to haemoglobin binding oxygen and CO2. $\endgroup$
    – Logan R. Kearsley
    Jan 4, 2019 at 23:11
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    $\begingroup$ A good transport molecule only weakly binds to the thing being transported. From that standpoint, the boranes don't look at all promising. $\endgroup$
    – Mark
    Jan 5, 2019 at 3:35
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Not having any clue where to begin on the problem of reversibly binding methane in some kind of protein complex, I'd suggest an alternative route to carrying metabolic gasses entirely: straight-up solubility.

Looking at your previous questions, it seems that your creatures are intended to use ammonia as a biosolvent. I have not been able to find solubility data on gaseous methane in liquid ammonia; if I had to guess, I would expect it to be slightly higher than the solubility of methane in water on Earth, since ammonia is slightly less polar than water and because the operating temperatures would be much lower (and/or the pressures would be higher). So, maybe you could get away with not bothering with a specialized gas transport molecule at all, and just letting methane diffuse directly into the blood plasma.

If, however, that is unacceptable, methane is more highly soluble in various lipids and other hydrocarbons. So, you could rely on whatever the boron-based equivalent of a lipid micelle, with a non-polar interior, is to dissolve methane when exposed to air in the lungs, and then allow it to slowly diffuse out as the micelles pass by methane-poor tissues.

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  • $\begingroup$ That is a very smart idea. I will look into that. $\endgroup$
    – Wither Fang136
    Jan 4, 2019 at 23:28

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