What could be used as an alternative to ATP in boron based biochemistry?

Question

I have created a life form that is based on the element boron. As a substitute for DNA it instead uses Diborane as a building block. I've come across a problem however that I can't seem to get around. This problem is what would these Boron cells use to obtain energy?

The atmosphere of the planet this creature lives in is heavily reducing. This means most of the oxidizing agents are locked up in bonds with other elements. This creature mainly breathes methane to power chemical reactions in a process of cellular respiration that looks like this.

4CONHNH₂NOHN₂ + 22CH₄ = 20NH₃ + 11C₂H₄ + 4CO₂

Methane is used to break down a chemical similar to carbohydrazide and is turned into ammonia, ethylene and carbon dioxide.

In carbon based biochemistry, the energy that allows this process to happen comes from ATP which is broken down in the process of hydrolysis, giving the cell energy. However, ATP is mostly carbon and oxygen based, which this boron based life form doesn't have a lot of. Knowing this, what could these boron based creatures use as an alternative to ATP?

Answer 1

The important part of ATP for energy storage isn't the carbon-based part: it's the phosphate chain. The adenosine part is essentially a nucleobase (adenine) bonded to a sugar--i.e., a fragment of an RNA molecule. That's a pretty suspicious coincidence, no? It seems likely that ATP derives from the ancient use of RNA as a catalyst, analogous to proteins, in addition to an information carrier.

So, what would be the analogous, ubiquitous structural base molecule in your boron biochemistry? I'd pick either a nucleobase or an amino-acid-equivalent (or something which can be both, like adenosine), and just stick a phosphate chain on it.

Edit: A reducing environment shouldn't be a problem for evolving phosphate chains... but a general lack of oxygen, or water for hydrolytic energy reactions, probably is!

However, these creatures do have lots of ammonia available, and -NH- groups are isoelectronic with -O- groups, so... This is considerably more speculative, but rather than HPO3 groups with an OH terminal, maybe P(NH)2(NH2) groups with an -NH2 terminal.

The ammonia equivalent of ATP hydrolysis and dehydration synthesis would be:

(NH2)-P(NH)(NH2)-(NH)-P(NH)(NH2)-(NH)-R + NH3 <-> P(NH)(NH2)3 + (NH2)-P(NH)(NH2)-(NH)-R

Where R is whatever "organic" base molecule you have to carry those phosphorus chains around.

Answer 2

2 carbon molecules.

@Logan R. Kearsley's idea of taking a page from your own fictional biochemistry makes sense. Here is another idea that will make sense to readers with only high school chemistry.

https://brilliant.org/wiki/common-types-of-organic-reactions/

The idea with ATP is that it takes energy to add that phosphorus and it will yield energy when you release it: energy currency.

Carbon-carbon bonds are the same way. It takes energy to expel that hydrogen and bond carbon to carbon. There is more energy in acetylene than in ethane, which is why we use acetylene for welding and ethane / methane for gas grills. On removing hydrogen, energy is stored. On adding hydrogen back to the carbon, energy is released.

Answer 3

Frame Challenge: Your organism will still be Carbon Based

When you say an organism is Carbon Based you are referring to the element that forms the core building block in your organic molecules.

Removing Carbon in favor of Boron Based Biochemistry has a whole slew of problems bigger than finding a solution for ATP, and it all leads back to the number of covalent bonds it can form. Carbon can form 4 covalent bonds whereas Boron can only form 3 without becoming unstable and negatively charged. This makes carbon far more useful in the construction of complex molecules. So much so, that evolution of your world would choose the carbon based path over the Boron based path, even if Carbon is less available.

Furthermore, your world actually has plenty of Carbon to work with. Organic carbon in our world mostly comes from the CO2 in our atmosphere; so, if your organisms are already relying on atmospheric methane in any substantial way, then the primary producers on your world can simply breath in methane, and breath out hydrogen gas as a way to bring carbon into your organism's natural life cycles.

The only reason for life to evolve not to be carbon based is if carbon is extraordinarily rare. Not just sequestered, but non-existent on your planet, and if Carbon in unavailable, the next logical step is the next densest element which can form 4 covalent bonds, that being Silicon. Even Germanium, Tin, or Lead based life may be more common that Boron based life because of how important that 4th covalent bond is in creating complex systems.

That said, Carbon based life is almost certainly the norm since we can prove it wins out, even against more prevalent options. Here on Earth, Carbon makes up only 0.02% of the elements in the crust whereas Silicon, the next best thing, makes up 28.2% of the crust. This demonstrates that life prefers the elements that work best over those that are just more common.