Hypothetical types of biochemistry

i know life on Earth is base on carbon,but is that really universal?
i meen,if the conditiona are right,life could be base on other biochemistry.
say:
Silicon

I think it's one of the most comon would be silicon. it is similar to carbon.it is in the same periodic table group.
i heard some microorganism have a large part silicon in compozition. is this true?

i have many other ideas about other types.
what do you think?

Here's some interesting pages about alternative forms of biochemistry. It's all very speculative though.

Silicon Based
Ammonia Based
Boron Based
Nitrogen Based
Posphorus Based

Ryag Han wrote:

i heard some microorganism have a large part silicon in compozition. is this true?

I haven't heard of anything like that, but I'm not much into biology. This would be very interesting if it is true though.

yup,it would enlarge our definision of life.

To me, silicon doesn't really seem all that promising for naturally-occurring lifeforms. The chemistry is similar to carbon's but there are important differences, especially regarding stability of various catenated molecules, and the Si=Si double bond.

While I would not rule out possibility of organisms whose chemistry is not based on organic molecules, it seems unlikely. The universe apparently forms many of the building blocks of such systems quite easily, the same does not seem to be so true for other postulated systems.

I have in mind the possibility of life that are based on, in carbon-poor systems, in chains of phosphorus and nitrogen (P-N). This chain made of phosphorus linked with nitrogen form stable compounds and could imitate the carbon-based substances, like proteins and acid nucleics.

Such type of life, to me, would not be like to be found in Earth-like conditions, but more certainly in colder planets with seas of a mixture of water-ammonia or pure ammonia in a reducing atmosphere rich in methane or ammonia. It would be soluble in ammonia mixtures because of nitrogen and phosphorus, that would be soluble in ammonia or aqua-ammonia, making a new possibility of alternative biochemistry.

hmm..phosphorus and nitroge.
that would be a wery alien system.
a silicon base life form would have a slowe metabolism.
but what about a P-N base life form?

Is it possible for life to be based on more than one element? And if so, what does "based" mean, when we say [element]-based life?

Some people say that phosphorus-nitrogen system are energy poor. But from what is this base? Maybe a P-N system could form, in alien environments, different molecules than just phosphorus-based acids. It would not form only rings, that are artificially made, but maybe also chains similar to amino acids or nucleic acids.

Phosphorus linked with nitrogen would form the main chains and phosphorus linked with oxygen molecules will be like phosfate, to produce energy. To me, P-N life could also use phosfate, as we use.

To me, phosphorus nitrogen beings would prefer to live in planets with average temperature of -50°C, with reducing atmospheres rich in methane, ammonia or phosphine, or even hydrogen (P-N life in gas giants). They would drink a mixture of water/ammonia or even pure ammonia. Or even HCN, but only at high pressure atmospheres. The air of such planets could also have NO2, NO3 or N2O rather than CO2.

Also, such worlds must orbit stars that emit almost no UV, since UV radiation would destroy the supply of methane or ammonia. Or even break NO2 or N2O. So such planets must orbit late K stars, quieter M stars or even brown dwarfs. Maybe brown dwarfs are perfect for such worlds, with no UV. UV light would be lethal to such creatures. And if exposed, they would melt like vampires when exposed to Sun!!! So such beings would prefer darkness or environments with much IR light, but not UV. Maybe blue light could also be dangerous to them, like UV to us, since blue light react with some substances, as far as I know.

If they see colors, they might see in the near IR spectrum or even visible light, since their planets would orbit cooler stars. And darkness would not be a problem to them, because since they are based on phosphorus, they would produce their own light! I imagine them as bright multicolored beings. Each cell of their bodies would shine in a different color, depending on the tissue. So they could see themselves in total darkness, like strange animals living deep in our oceans! Maybe even after death their cells could still continue to shine, for some time.

Not only animals, but also plants and every living organism would shine in a particulary range of colors. From space, the vegetation areas of such worlds would be bright, maybe brighter than rocks, or even ice!

Near K stars, G stars and F stars would turn such worlds into something like Titan. But it would destroy ammonia, that would be a perfect source of energy to such beings, based on nitrogen and phosphorus, not carbon.

To me, life is not based on a single element. Oxygen and nitrogen are also as common as carbon in our biochemistry. We are based on carbon, but also on hydrogen, oxygen, nitrogen, sulfur and phosphorus. We may even have more oxygen than any other element in our bodies!

So to me the idea that life is based on carbon is an old paradigm that should be descarted, because we are based much more than one element.

In case of alien life, they only would use a different system of molecules, but the elements would be the same that we use. Some or other minor elements that would be different, but the main elements would be the same.

In the case of phosphorus-nitrogen life, they even could use carbon being part of their structure and energy source.

http://en.wikipedia.org/wiki/Hypothetical_types_of_biochemistry

Why not carbide? Silicon+Carbon-based life.

Yes, maybe it could be possible. But still would have much carbon, being carbon-based life that only use silicon as an additive.

Different types of speculative biochemistries of alien life forms that differ radically from those known on Earth.
But these are not based on facts or investigations.
Thus, I don't believe on this hypothetical.