Steve Jackson Games - Site Navigation
Home General Info Follow Us Search Illuminator Store Forums What's New Other Games Ogre GURPS Munchkin Our Games: Home

Go Back   Steve Jackson Games Forums > Roleplaying > GURPS

Reply
 
Thread Tools Display Modes
Old 06-05-2012, 12:23 AM   #21
Anthony
 
Join Date: Feb 2005
Location: Berkeley, CA
Default Re: [Build Advice] Model Anaerobic/Aerboic Breathing?

Quote:
Originally Posted by Ashtagon View Post
I'm confused on this point too. Afaik, the only natural organic reaction that produces O2 and consumes CO2 is photosynthesis, found in plants (which incidentally also do the O2->CO2 reaction at the same time, but in different areas). I'm not seeing anything that implies these creatures are photsynthesising.
The original post mentioned acetogenesis, which consumes H2 and CO2, though based on this I think both are intermediate steps in the process, not feedstock. In any case, such a metabolism would be (a) very slow, and (b) almost certainly poisoned by oxygen.
Anthony is offline   Reply With Quote
Old 06-05-2012, 05:58 AM   #22
Sunrunners_Fire
 
Join Date: Mar 2010
Default Re: [Build Advice] Model Anaerobic/Aerboic Breathing?

Quote:
Originally Posted by Ashtagon View Post
I'm confused on this point too. Afaik, the only natural organic reaction that produces O2 and consumes CO2 is photosynthesis, found in plants (which incidentally also do the O2->CO2 reaction at the same time, but in different areas). I'm not seeing anything that implies these creatures are photsynthesising.
I compartmentalize my questions, usually.

I have about six pages of typed notes sitting in local documents and another dozen/ish pages of handwritten notes. It isn't practical to post all of that every time I have a question about how to model something in game terms. It would only be confusing (especially as its' rather subject to change). In this case, I asked about how to model (the current version of) their respiration. Photosynthesis isn't respiration. Though, yes, the Mnemi do possess an assortment of autotrophic features in a variety of flavors. Its' not relevant to the question though; or at least I didn't think it was. :grins:

Quote:
Of course, if this is intended to be a "ignores science" racial feature, carry right on :)
Such is not the intent, no. Bend it some, sure. I know that I'm engaging in a number of data errors; some intentionally, but mostly by accident. Its' a learning exercise.

Quote:
Originally Posted by Anthony View Post
The original post mentioned acetogenesis, which consumes H2 and CO2, though based on this I think both are intermediate steps in the process, not feedstock. In any case, such a metabolism would be (a) very slow, and (b) almost certainly poisoned by oxygen.
Google notes facultative acetogenic bacteria as existing in the here and now. If its' poisoned by oxygen, its' an obligate anaerobe not facultative. Various things note that there are only bacterial examples of acetogens known on Earth, but I don't believe its' physically impossible for them to become larger/more-complex than that.

Also, methanogenesis is different than acetogensis. They're both carbonate reduction but the products are different. (Methanogenesis is used by (some? all?) archaea and results in methane/CH4; acetogenesis is used by some bacteria and results in acetate.)
Sunrunners_Fire is offline   Reply With Quote
Old 06-05-2012, 08:30 AM   #23
David Johnston2
 
Join Date: Dec 2007
Default Re: [Build Advice] Model Anaerobic/Aerboic Breathing?

Quote:
Originally Posted by Anthony View Post
The breathing CO2 part to exhale oxygen is almost certainly energy-negative even counting in the food.
Plants do it, although of course they do it by not being very active.
David Johnston2 is offline   Reply With Quote
Old 06-05-2012, 08:34 AM   #24
gjc8
 
Join Date: Oct 2005
Default Re: [Build Advice] Model Anaerobic/Aerboic Breathing?

The basic model of acetogenesis, as I understand it, takes in carbon dioxide and hydrogen and spits out acetic acid and water, not oxygen. The energy source here is really the hydrogen, not the carbon dioxide, though I think both are actually generally intermediates in actual organisms.

If you have another carbon source, like food, I can't imagine that using carbon dioxide as a feedstock makes much sense. Perhaps it would help to actually write out the basic chemical equation for what you imagine is happening, which would allow you to work out an energy balance for it.

Regular respiration, for example:

C6H12O6 [glucose] (-1271 kj/mol) + 6 O2 (0 kj/mol) -> 6 CO2 (-393 kj/mol x 6) + 6 H20 (-242 kj/mol x 6) + 2539 kj/mol

Now, if I were designing an anaerobic heterotroph, I might say that, as long they're well fed, they don't need to breath at all, based on fermentation:

C6H12O6 (-1271 kj/mol) -> 2 C2H6O [ethanol] (-277 kj/mol x2) + 2 CO2 (-393 kj/mol x2) + 69 kj/mol

Note the drastically reduced energy yield per mole of glucose. So, in GURPS terms, this could be Doesn't Breath (Temporary Disadvantage: Increased Consumption 5 -50%), which implies that you need to eat a full meal for every 15 minutes you go without air.

Alternatively, I might say you breath hydrogen.

C6H12O6 (-1271 kj/mol) + 12 H2 (0 kj/mol) -> 6 CH4 (-75 kj/mol x 6) + 6 H20 (-242 kj/mol x 6) + 631 kj/mol

If you also had CO2, you could use this energy to run respiration in reverse. But there's no reason to unless you need molecular oxygen for some reason; you'd burn more glucose than you'd get back.
gjc8 is offline   Reply With Quote
Old 06-05-2012, 08:41 AM   #25
RyanW
 
RyanW's Avatar
 
Join Date: Sep 2004
Location: Southeast NC
Default Re: [Build Advice] Model Anaerobic/Aerboic Breathing?

Quote:
Originally Posted by David Johnston2 View Post
Plants do it, although of course they do it by not being very active.
And they also have to absorb energy from the environment (i.e. energy negative). CO2 can be thought of as a dead battery of the chemical world.
__________________
RyanW
- Actually one normal sized guy in three tiny trenchcoats.
RyanW is offline   Reply With Quote
Old 06-05-2012, 08:41 AM   #26
gjc8
 
Join Date: Oct 2005
Default Re: [Build Advice] Model Anaerobic/Aerboic Breathing?

Quote:
Originally Posted by David Johnston2 View Post
Plants do it, although of course they do it by not being very active.
And also having the sun to use as an energy source.
gjc8 is offline   Reply With Quote
Old 06-05-2012, 09:00 AM   #27
gjc8
 
Join Date: Oct 2005
Default Re: [Build Advice] Model Anaerobic/Aerboic Breathing?

Quote:
Originally Posted by RyanW View Post
CO2 can be thought of as a dead battery of the chemical world.
Well, the dead battery of the organic chemistry world, anyway.
gjc8 is offline   Reply With Quote
Old 06-05-2012, 09:09 AM   #28
Bruno
 
Bruno's Avatar
 
Join Date: Sep 2004
Location: Canada
Default Re: [Build Advice] Model Anaerobic/Aerboic Breathing?

Quote:
Originally Posted by gjc8 View Post
And also having the sun to use as an energy source.
The AND part is important. Photosynthesis is SO energy consuming the plant doesn't have enough energy left over to support an energetic lifestyle at all. Even "active" plants like venus flytraps aren't very active, and perform most or all of their motion through a really clever use of elasticity. Basically venus flytraps "wind up" the "spring" mechanism for their leaves through slow growth, taking days to reset.
__________________
All about Size Modifier; Unified Hit Location Table
A Wiki for my F2F Group
A neglected GURPS blog
Bruno is offline   Reply With Quote
Old 06-05-2012, 10:55 AM   #29
Anthony
 
Join Date: Feb 2005
Location: Berkeley, CA
Default Re: [Build Advice] Model Anaerobic/Aerboic Breathing?

Quote:
Originally Posted by Sunrunners_Fire View Post
Google notes facultative acetogenic bacteria as existing in the here and now. If its' poisoned by oxygen, its' an obligate anaerobe not facultative. Various things note that there are only bacterial examples of acetogens known on Earth, but I don't believe its' physically impossible for them to become larger/more-complex than that.
It's quite low energy compared to the oxygen reactions.
Anthony is offline   Reply With Quote
Old 06-05-2012, 11:45 AM   #30
Sunrunners_Fire
 
Join Date: Mar 2010
Default Re: [Build Advice] Model Anaerobic/Aerboic Breathing?

Quote:
Originally Posted by Anthony View Post
It's quite low energy compared to the oxygen reactions.
Yep.

The stuff I'm reading tells me that most/all of the anaerobic methods generate 2 ATP per, while the aerobic method generates 30/ish ATP per (theoretically up to 38 ATP though nothing on Earth does that level of efficiency). Aerobic is up to 15 times more efficient than Anaerobic.
Sunrunners_Fire is offline   Reply With Quote
Reply

Tags
alien, aliens, anaerobic, build advice, doesn't breathe, increased consumption

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Fnords are Off
[IMG] code is Off
HTML code is Off

Forum Jump


All times are GMT -6. The time now is 06:16 AM.


Powered by vBulletin® Version 3.8.9
Copyright ©2000 - 2024, vBulletin Solutions, Inc.