Why do all living things have to have Carbon and Water in them?

Question

What's so special about Carbon, Hydrogen and Oxygen that they end up in everything that's organic?
If there is life on other planets could it be made up of different elements?

Answer 1

Carbon, hydrogen and oxygen are excellent atoms for forming complex chains of carbohydrates - the building blocks of life. The bonding sites on these atoms form very strong links to other atoms and help facilitate molecule cohesion. It has been hypothesized that silicon based life could exist, but there is no known example of this on earth. Simply put, the three atoms you mention are in such large supply that is just makes sense that they would be used in life as they comprise a great deal of the matter in the universe.

Answer 2

SF writers have been mulling over this issue for decades. The only life-forms we know of are those here on Earth and as you say, we're all carbon based.

So far nothing has been found on Mars - if anything is found, I suspect it will not be much more than a green slime clinging to a bunch of rocks somewhere. Problem is temperatures on Mars seem to fluctuate from freezing cold to ultra-freezing cold with not a lot of heat.

Heat is the operative word as far as 'life' is concerned. Some sort of hot soup in which life can start.

SF is used as a platform to float ideas. This is because SF is just that, fiction. It means then that real scientists who can write in novel form, can float their ideas to a wider public and get some feed-back.

By reading enough SF you could possibly find someone who has got a theory, albeit an SF theory of what lifeforms across the galaxy may be like and made of.

One possible source of scientific information which is sometimes slightly outside where the 'priesthood' is going, are mags such as New Scientist. Have not read it for decades, but back in the 60s they published an article which explained in graphic detail how 'mana' was made to feed the Israelites in the desert.

Remember that? Mana from heaven. What was that and how? Okay so the New Scientist mana machine was a spoof but to the untrained brain [mine] it seemed plausible.

What if mana was made of a non carbon based non organic material which was/is edible? And, does it come in waffer form? Or, does it just look like snow flakes?

Answer 3

Living beings are made up of complex and large compounds. Of all the elements only Carbon can form stable bonds with itself and can continue this process infinitely. This Carbon framework provides the basis for other elements to interact with each other and thus produce what we call life.

Hydrogen apart from forming a stable bond with Carbon does not form a bond so strong that it cannot be broken. This is vital so that the reactions do occur.

It is possible that life could be based on other elements. Silicon, in the same group as carbon can form vast chains of the unit (Si-O-Si). S also can form bonds with itself but not as large as Carbon.

Answer 4

There are various theories, and the simplest one of them all is - you guessed it - God wants it that way, no more research or science necessary (cheap and easy isn't it?).

Want a better answer? Well there are a few theories around. A similar question to yours would be 'why are living things on this planet carbon-based instead of silicon-based, despite those two elements being so similar in characteristics?'.

Apart from being so abundant on this planet, carbon also has other advantages over other elements. For example, on its outtermost shell it has FOUR electrons, making it possible to bind with a large number of other elements (primarily oxygen, hydrogen, nitrogen and to a lesser extent, other non-metals). If you look at the human body, you'll find that amino acids (the 'buidling blocks of life', are made of those four primary elements).

'But so can silicon' I hear you ask. Bare in mind that the 4 valence electrons are much closer to the nucleus than those on Silicon, and they are therefore held much more strongly together by electromagnetic forces and therefore gives overall more stable covalent bonds. What's more, since it tends to have a charge of zero (like that of the noble gases), it is also a naturally stable compound and therefore can exist in its pure form (think graphite, diamonds), whilst dynamically allowing greater flexibility to react and form new compounds (as oppose to hydrogen and sodium, which are highly reactive elements that it's almost impossible to find them exist as 'pure forms' in nature. e.g. it's not very easy to break water down to extract hydrogen).

Hope this helps!

PS: edit - sorry only answered half the question.

Water has a few characteristic making it a must (or almost must) on this planet because:

1. It's a good solvent. A lot of things needs to be in solution in order to work as, say, an electrical conductor. Perfectly dry table salt can't really conduct electricity because it has no free-flowing, charge particles and therefore it must be dissolved to form charged ions in order to be a good electrical conductor. (More complex things like ATP and ADP and all those things in physiology are also examples of reactions that must occur in an aqueous media).

2. It has high thermal capacity. Imagine if there's nothing to hold the heat produced by your body - you won't be able to stop eating for one second! If you boil a glass of water, you will find that it takes quite some time for it to completely cool down to room temperature again, as oppose to touching a steel rod, which is always icy cold (because it conducts heat really well and doesn't retain much).

3. It has flexible physical properties - liquid, gas, and solid. That makes it possible to fulfil a number of roles, e.g. blood as a transport system in your body, whilst it can be exhaled as a vapour (which keeps ur airways moist and open).

Enough reasons?!?! Have a good day!

Answer 5

It's possible that they could live off of other basic elements but unlike the other nose-pickers for answerers above me I know that scientists don't know of any other way, so they have to search for what they know life *can* work with which is water and carbon.

Answer 6

I think that life on other planets does not neccessarily require these elements. When we go searching on Mars for example, for life, we look for signs of water. Do you really think that the organisms on Mars live in exactly the way we do? No. They have different environmental conditions that they must be adapted to, and could therefore easily consist of other elements.

Answer 7

That isn't entirely true. There are sulfur based life forms found in deep caverns on the ocean floor. Life is made of what is available.

Carbon creates strong bonds, and is highly attracted to oxygen molecules.

Answer 8

As far as we know these make up the basis of life. Some far distant world this may not be the case?

Answer 9

there r laws in the world which called Physical Laws. and physical laws can't be broken.