[Build Advice] Model Anaerobic/Aerboic Breathing?

[Sunrunners_Fire]

Okay, so ... I have this alien species. (hehe) The question at hand is "How do I model their respiration?" A tag search and forum search came up blank, so ...

[What is being modeled]

"Mnemi are facultative anaerobic organisms which primarily utilize acetogenesis for their respiration -- they can utilize aerobic respiration as circumstances warrant it; the presence (or lack thereof) of oxygen doesn't harm them." In practice, this means they breathe both carbon dioxide and oxygen, though they continue to breathe if there is no carbon dioxide and they continue to breathe if there is no oxygen; that breathing purely carbon dioxide results in them exhaling oxygen; that breathing purely oxygen results in them exhaling carbon dioxide; and all of these things mean that they'll breathe just fine as long as they have either or both available. Assuming they meet the other requirements for breathing (food and water are important parts of breathing!), of course.

[How do I model it]

Breath-Holding won't work for this. Doesn't Breathe also doesn't work, even when modified, as none of the existing modifications cover this. I could just describe it as a Perk, but it gives more benefit than I'd expect a Perk to give. You can seal a human and a handful of mnemi in a small air-tight room; they'll keep breathing just fine until they start dropping from dehydration and starvation. Yes, even the human will be fine (though the mnemi will start dropping before the human does).

I'm either missing something or I need to get creative. Suggestions? Did I miss a relevant thread or post when searching?

(EDIT) ... and I misspelled the thread title. Eww.

[Ulzgoroth]

Uh, not exactly answering your question here, but can you clarify the biochemistry you're using? I'm not seeing how you could wind up inhaling carbon dioxide and exhaling oxygen.

I'd think this is a fairly minor advantage, points-wise, since it doesn't really change the breathing rules, it just means you can breathe in two atmosphere types rather than one. Breathing a different atmosphere instead of human-normal is a zero-point feature. As such I'd be tempted to rate it as a perk, though that might be too low.

[ericthered]

The real advantage I see in this is that you can't suffocate them. If they can both convert O2 to CO2 and vica versa, they don't have to breathe in new air at all. they just take a breath, and turn all the O2 to CO2, and then turn the CO2 to O2.

In all honesty, I'd rather say, based on my understanding of aerobic/anaerobic metabolisms, that they can efficiently burn energy by either using an efficent oxygen burn, or an inefficient anaerobic burn.

This gives them "doesn't breathe" with the temporary disadvantage "Increased Consumption", as they have to eat more to get the same energy from the burn.

[Langy]

Can they just breath their own exhalations? If so, I'd call this a modified Doesn't Breath. Somewhere between -20 and -50%, I'd say.

[Refplace]

Originally Posted by ericthered

This gives them "doesn't breathe" with the temporary disadvantage "Increased Consumption", as they have to eat more to get the same energy from the burn.

I think this most closely handles it, especially if its a scifi rather then fantasy race.
Though I like the idea of such a race as Dwarven mining companions.
I probably would replace mana sensitive as the temp disad there though.
Also tack on another limitation for needs one or the other.
However what if they are mostly oxygen but can live off CO2 for a short time? That could be handled as Breath Holding with temp disad or accessibility.

[Anthony]

This is Violates The Second Law of Thermodynamics with the specialization of "Doesn't Breathe", and maybe a small enhancement for oxygen generation though in practice it seems unlikely to ever matter.

[Ulzgoroth]

Originally Posted by Anthony

This is Violates The Second Law of Thermodynamics with the specialization of "Doesn't Breathe", and maybe a small enhancement for oxygen generation though in practice it seems unlikely to ever matter.

It's not violating the second law of thermodynamics that I can see. The gas exchange involved doesn't make sense, but the metabolism is burning energy all along the line.

[Anthony]

Originally Posted by Ulzgoroth

It's not violating the second law of thermodynamics that I can see. The gas exchange involved doesn't make sense, but the metabolism is burning energy all along the line.

The breathing CO2 part to exhale oxygen is almost certainly energy-negative even counting in the food.

[Sunrunners_Fire]

Originally Posted by Ulzgoroth

Uh, not exactly answering your question here, but can you clarify the biochemistry you're using? I'm not seeing how you could wind up inhaling carbon dioxide and exhaling oxygen.

I am neither a biologist nor a chemist and as such it is entirely possible that I'm misunderstanding what I'm reading. As such? Good question. I'm still working out the process myself. I know the initial state and I know the final state and I'm working my way through the process as time allows.

Once (if) I finalize the process involved, I'll be sure to post the results.

I'd think this is a fairly minor advantage, points-wise, since it doesn't really change the breathing rules, it just means you can breathe in two atmosphere types rather than one. Breathing a different atmosphere instead of human-normal is a zero-point feature. As such I'd be tempted to rate it as a perk, though that might be too low.

One vote for it being a perk.

Originally Posted by ericthered

The real advantage I see in this is that you can't suffocate them. If they can both convert O2 to CO2 and vica versa, they don't have to breathe in new air at all. they just take a breath, and turn all the O2 to CO2, and then turn the CO2 to O2.

In all honesty, I'd rather say, based on my understanding of aerobic/anaerobic metabolisms, that they can efficiently burn energy by either using an efficent oxygen burn, or an inefficient anaerobic burn.

This gives them "doesn't breathe" with the temporary disadvantage "Increased Consumption", as they have to eat more to get the same energy from the burn.

They have increased consumption already as breathing carbon dioxide is their preferred respiration; oxygen respiration is for when they start running low on the needed resources (or low on carbon dioxide).

One vote for a modified Doesn't Breathe.

Originally Posted by Langy

Can they just breath their own exhalations? If so, I'd call this a modified Doesn't Breath. Somewhere between -20 and -50%, I'd say.

Another vote for a modified Doesn't Breathe.

Originally Posted by Refplace

I think this most closely handles it, especially if its a scifi rather then fantasy race.
Though I like the idea of such a race as Dwarven mining companions.
I probably would replace mana sensitive as the temp disad there though.
Also tack on another limitation for needs one or the other.
However what if they are mostly oxygen but can live off CO2 for a short time? That could be handled as Breath Holding with temp disad or accessibility.

And another vote for Doesn't Breathe. It is a science-fiction species. I'd not bother trying to work out the biochemistry for a fantasy race.

[Sunrunners_Fire]

Originally Posted by Anthony

The breathing CO2 part to exhale oxygen is almost certainly energy-negative even counting in the food.

Erm. Hydrogen (from water) can be combined with carbon dioxide to produce glucose and oxygen. Where do you think the oxygen you are breathing comes from?

(For the record, I'm cutting out a lot of the details of the Mnemi simply because I didn't think they were relevant to the question of "How do I model their respiration in GURPS terms?" :grins: )