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Vertigo
2004-Dec-22, 04:55 PM
OK maybe I do watch a lil bit too much Star Trek but on with my question,

Are Lifeforms restricted to only being 'carbon-based' that we know of - appologies in advance if I have failed to realise anythin else.

Also ( maybe this is the wrong place to ask this but... ) Why are we Carbon-based - as many aspects of that question as u care to answer plz.

I hope i havent been too ignorant ( as u can tell, this is me first post :-) )

TIA

antoniseb
2004-Dec-22, 05:07 PM
Originally posted by Vertigo@Dec 22 2004, 04:55 PM
Why are we Carbon-based?
First, welcome to the forum. You could have posted this here or in the Life in Space section. Either is fine.

We are carbon based because of the rich diversity of chemistry that is possible with organic [carbon-based] chemistry. There is nothing that would completely rule out the development of self-replicating complex chemistry with some other basis, but it does seem unlikely at the moment, and would probably have to happen in a place where there was practically no Carbon.

ChromeStar
2004-Dec-22, 05:18 PM
Waz up Vertigo

did you get your name from U2 new song or what? :D

as far as i'm aware we develped into carbon based life forms due to carbon being a exellent material for the job never mind it is the most abundent. it has qualities that help with the types of bonds needed to form and build life like ourselves.

As for "could we have been made of any thing else?" - yes according to scientists
silicon could have been a much more suitable material because it 's much stronger, yet it shares almost the bonding qualities carbon does.

they're even considering using silicon in place of carbon should one day minds are tranplanted into new bodies - thay'll use it to build a better artificial body with the same qualities of the human body.

also i see nothing ignorant with question. :D

bossman20081
2004-Dec-22, 07:09 PM
Theres nothing wrong with this question, Vertigo. (BTW Welcome to the forums)

As said before, we're carbon based because of how flexible carbon is-it can bond and interact with a lot of things most materials cant.

I dont know if this is true, but I've always felt that we're carbon based and not silicon based because carbon is a much simpler substance (carbon's atomic number is 6 while silicon is 14. Anton, could you tell me is this is true?

Tinaa
2004-Dec-22, 07:32 PM
Carbon has four valence electrons so it easily works with other atoms. Its oxidation number is either +4 or -4. Quite a friendly little element.

antoniseb
2004-Dec-22, 07:33 PM
Originally posted by bossman20081@Dec 22 2004, 07:09 PM
Anton, could you tell me is this is true?
I would have to look this up the same as anyone else here. Yes Silicon has 14 protons, but that doesn't make it more complex. It has four valence electrons, just as Carbon does, but I don't think it can be simply substituted for Carbon in a molecule. These electrons are on top of a full shell of eight, which may affect how the atom bonds. Is there such a thing as an all Silicon equivalent of a benzene ring? Is there such a thing as a silicon nanotube? I'm no expert on silicon chemistry.

Duane
2004-Dec-22, 09:49 PM
As for "could we have been made of any thing else?" - yes according to scientists
silicon could have been a much more suitable material because it 's much stronger, yet it shares almost the bonding qualities carbon does.

Well, no actually, silicon is not a more suitable material. This is a quote from a post by Tim Thompson in this thread: http://www.universetoday.com/forum/index.p...=15&#entry32740 (http://www.universetoday.com/forum/index.php?showtopic=3332&st=15&#entry32740)


The reason for this is that, while silicon (Si) has 4 bonding electrons available, like carbon ( C ), Si is a bigger atom; it makes longer & weaker bonds. One result of this is that Si only makes single bonds, while C will double bond. So, for instance CO2 is a closed shell molecule, because the C has double bonded to each of the O, whereas SiO2 has only two single Si-O bonds, and still has two electrons available to bond. So the Si electrons aren't used up until you get SiO4, but since the bonds are single, SiO4 has 4 loose electrons looking for bonds, one for each O atom. The bottom line is that Si forms crystals with O and does nothing greatly interesting with H. On the other hand, C forms a gas with O (CO or CO2), and creates a suite of noncrystalline molecules that are the basis of organic chemistry. If you create a definition of "life" that is sufficiently non-commital as to exactly what "life" is, then perhaps you can claim that Si based life can exist ("living crystals" that transmit information by moving crystal defects). But that is not "life as we know it".


So, to be succinct, Carbon is a far better material to use if you want to give rise to life. That is not to say that silicon can't ever be the base, it simply means that carbon is better and more likely to form the basic molecules necessary for life.

Nyrath
2004-Dec-23, 12:15 AM
http://www.projectrho.com/rocket/rocket3aa...l#notasweknowit (http://www.projectrho.com/rocket/rocket3aa.html#notasweknowit)

zephyr46
2004-Dec-23, 04:23 AM
I always find this an interesting discussion, because it leaves out how much water we are made of, and calcium.

Not being a chemist, I am wondering why we are refered to as being "carbon based"?

And welcome Vertigo. No such thing as a dumb question, just a question not asked :)

ChromeStar
2004-Dec-23, 08:23 AM
Hi all

Based on a program i saw a possible reason carbon is "used" is becuase silicon is far less abundent there just is'nt enough on earth, however if there were more, life could have been built of silicon.

P.s. intresting Duane, i did'nt know that! :)

Vertigo
2004-Dec-23, 08:52 AM
Okies, Spanx all for your Welcome msg and for all your answers.

Duane, does that mean then if Si has spare Electrons that there would be more possibilities for bonding in a way that Carbon wouldnt be able to ?

eburacum45
2004-Dec-23, 01:28 PM
Originally posted by ChromeStar@Dec 23 2004, 08:23 AM
Hi all

Based on a program i saw a possible reason carbon is "used" is becuase silicon is far less abundent there just is'nt enough on earth, however if there were more, life could have been built of silicon.


no, that is not right; silicon is locally abundant in the Earth's crust, and there is in fact much more silicon than carbon on the surface of our planet.

Two reasons suggest that silicon would not be a good basis for life;
first the oxidised form of silicon is a solid at earth-like temperatures, so any creatures would breath out silca sand rather than carbon dioxide; second, the range of biochemistry using silicon is considerably smaller than that possible with carbon.

However it might be the case that a silicon biology is possible in hot or molten environments- although the viscosity of lava would make any hot silicon beasts very slow moving indeed...

Tinaa
2004-Dec-23, 05:04 PM
Not being a chemist, I am wondering why we are refered to as being "carbon based"?

Even our DNA has carbon. Deoxyribonucleic acid is made up of a ringed 5-carbon sugar, phosphate group and nitrogen base.

Here is the equation photosynthesis:

6CO2 + 12H2O + light energy ---> C6H12O6 + 6O2 + 6H2O

Here is cellular respiration in animals:

C6H12O6 + 6O2 ---> 6CO2 + 6H2O + Energy

Carbon is in everything. The nitrogen bases in DNA are pairs: adenine & thymine or guanine & cytosine.

Look at the chemical formulas of the parts of DNA:

Adenine: C5H5N5

Guanine: C5H5N5O

Cytosine: C4H5N3O

Thymine: C5H5N2O2

Phosphate: PO4

2-deoxyribose: C5H9O4

As you can see at the cellular level, carbon is the "base" of all the molecules used in the processes of life as we know it. I didn't include uracil which is used in RNA, but it is also "carbon based."

bossman20081
2004-Dec-23, 05:43 PM
Just adding on to what Tinaa said, every organic substance has carbon in it, and since life is made of organic substances, we are carbon based. And also, water is a compound, not an element, so I wouldnt think that would be a base.

Thanks anyway, Antonsieb.

Tinaa
2004-Dec-23, 07:06 PM
No, water is not a base. Water is needed for life as we know it.

ChromeStar
2004-Dec-23, 09:52 PM
The evidense seems to be mounting that i'm incorrect perhaps i misunderstood the info i got. :huh:

Where do you all get your info, i'd like to learn more. :)

Thanx in advance!!! :D

ChromeStar
2004-Dec-23, 10:00 PM
Tinaa's Right

without water all process in the body of any living thing would stop functioning, just the most basic functions like transportation of good and bad substances would already lead to death!!!

Tinaa
2004-Dec-24, 04:03 PM
The NASA Astrobiology Institute was also wondering about silicon based life. Seems that carbon has all the advantages. Carbon can link in a variety of ways like long chains, ring structures, or gas compounds. Carbon is much more abundant than its sister silicon. The biggest difference seems to be that carbon can form right or left handed molecules and silicon cannot.

Here is the link: http://nai.arc.nasa.gov/astrobio/feat_ques...ilicon_life.cfm (http://nai.arc.nasa.gov/astrobio/feat_questions/silicon_life.cfm)

ChromeStar
2004-Dec-24, 04:17 PM
Danm!!!... thats a good link!!! :D

Does anyone know where to find all te Nasa links?, cos whenever i search with google or something or type into my browser www.Nasa.gov, i can never find what i'm looking for. :huh:

galaxygirl
2004-Dec-24, 05:35 PM
What kind of NASA links are you looking for?

NASA's homepage is http://www.nasa.gov/home/index.html, and you can use the search feature at the top right hand corner of that page to find links.

ChromeStar
2004-Dec-24, 05:41 PM
Thanx galaxy girl

i'm trying to find the nasa home page.

and thats the link :D