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Why Water?

  1. May 30, 2005 #1
    Howdy first post. Why is it said that life needs water to develop. Everybody says that life hear came from the sees but why could it come from a methane sea? or even beyond that on a gas planet?
    Thanks Ryan
     
  2. jcsd
  3. May 30, 2005 #2
    i'd like to know this aswell, please awnser
     
  4. May 30, 2005 #3

    Monique

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    Water is a great solvent with a high di-electric constant.
     
  5. May 30, 2005 #4
    Why would that eliminate all others?
     
  6. May 31, 2005 #5
    It would be important that the medium would allow many different chemical reactions to occur, as life is somehow a complicated chemical balance.
     
  7. May 31, 2005 #6

    DaveC426913

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    Water is an incredible substance.
    - It is one of the few chemicals that have a broad temp. range of liquid state. This allows for excellent chemical interaction.
    - It is an almost universal solvent. It can dissolve most things, including rocks containing minerals that life needs.
    - It is one of the lightest molecules in existence. (atomic weight of 10).
    - it has a very high heat capacity, meaing it absorbs and holds heat extremely well.
    - Its solid state is more bouyant than its liquid state - large bodies will freeze from the surface down, unlike all other liquids, which will freeze from the bottom up. Large bodies of water are protected from freezing, allowing life to exist and fluorish though winters.

    The list goes on and on. Some day, I'll compile a list of things that make water an excellent choice for life, beating out all others.

    (Another list shows why carbon is an equally excellent choice for the basis of life. It is unique in the periodic table.)
     
  8. May 31, 2005 #7
    while we're on it, why is Oxygen so wonderful, this might be a chemistry question, but why is it so important to combustion, and equally, why is it so important to life???
     
  9. May 31, 2005 #8

    DaveC426913

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    A factor to consider when examining chemical constituents of molecules is that all elements are not created equal (I mean in terms of usefullness). The universe is strongly biased towards those elements nearest the beginning of the table, where elements are light, strongly interactive, flexiable and abundant. As we get into heavier and heavietr elements, the combinations are less varied and less interesting.

    Thus:
    Hydrogen: really light, really useful,
    Helium: inert,
    Lithium, Boron, Beryllium: (I dunno, good question),
    then the really intreresting ones: Carbon, Nitrogen, Oxygen,
    As you go up the table, the roles filled by heavier elements can more efficently be filled by lighter ones, where you get more bang for your buck.

    Re: Oxygen. With the exception of fluorine (and inert helium), Oxygen is the lightest, and rightmost element on the table. It combines with Hydrogen, the lightest and leftmost element on the table, and the most abundant element in the universe. These two opposites combine with the greatest release of energy, which means they provide the biggest bang for the buck. (and which is why they're what is used in rockets).

    So, this begs the question:
    Obviously my logic is shaky. Why do lithium, boron and beryllium, as well as fluorine play relatively small roles in chemistry (compared to H, C, N, O)?
     
  10. May 31, 2005 #9
    I know oxygen can help people live. People breathe in oxygen.
     
  11. May 31, 2005 #10
    I think all chemical elements play equal inportant roles in the Universe, only when people need some of them, then those become more important than others.
     
  12. May 31, 2005 #11

    DaveC426913

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    Well...

    oxygen and hydrogen were powering life on Earth long before humans came along to decide what was or wasn't important.

    Hydrogen and helium were powering every star in the universe long before Earth was even a dustball.

    I feel comfortable saying that hydrogen plays a more important role in the universe than, say, yttrium.
     
  13. May 31, 2005 #12
    I would think it because water is the reagent which hydrolyses majority of organic substances into smaller amino acids/carbohydrates/whatever, and also in the opposite case, where condensation (in most cases produce H2O) allows peptide bonds/Phosphodiester bonds/glycosidic bonds/ester bonds to form.

    Self-relicating molecules are the key to life, and since H2O plays 'I break you up or join you together!' part, it would be pretty important.
     
  14. May 31, 2005 #13

    Hurkyl

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    IIRC, oxygen isn't important to life in general -- just life adapted to breathing oxygen. We didn't really have much oxygen in the atmosphere until some organisms started producing it to poison off the competition...

    (I suppose there might be an argument it's important for more complex lifeforms, though, but I can't make that one!)
     
  15. May 31, 2005 #14

    Phobos

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    It doesn't eliminate other possibilities. It's just much more likely, given what we know about life & biochemistry.
     
  16. May 31, 2005 #15

    Phobos

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    oxygen is one of the most efficient "electron acceptors"

    ...if I had the time, I'd dig up a comparison to other types of electron acceptors which can be used
     
  17. May 31, 2005 #16

    Monique

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    The problem with oxygen is that it forms free radicals, very toxic to life. Oxygen is a very good electron acceptor, as Phobos said, but the release of energy from oxygen is very explosive; the energy that can be extracted from it would be very inefficient without the electron transport chain in the mitochondria, which tap the energy step by step.
     
  18. Jun 1, 2005 #17
    Hello, momique, I think only under some specil condition will oxigen form radicals, or all of us should not live same this. conluson oxygen dangeros to life is not true. u think so too, i know that.
     
  19. Jun 1, 2005 #18

    Monique

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    Not true, we have a whole system of anti-oxidants in our system. An example I can give you is superoxide dismutase, an enzyme that catalyzes the dismutase reaction of toxic superoxide radicals to molecular oxygen and hydrogen peroxide. Oxidative stress is one of the reasons why we get old, people living at great hights are said to live longer, due to the lower oxygen tension.
     
  20. Jun 1, 2005 #19

    Monique

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    The special condition is in the mitochondria, along the respiratory electron transport chain. Electrons formed during the oxidation of glucose are passed along the electron transport chain to electron accepting molecules embedded in the mitochondrial membrane. These molecules then produce free protons, which ultimately drive ATP synthesis.

    In the final step of electron transfer, electrons combine with oxygen and protons to produce water. It is possible that by mistake the electron is accepted by molecular oxygen (O2), leading to the formation of superoxide free radicals (O2.-). It is said that this electron leak converts about 1-3% of oxygen molecules into superoxide.

    AND you must know that neutrophil cells of the immune system use respiratory burst to generate a large quantity of free radicals. These are packed in granules and released to the outside of the cell to kill bacteria.
     
  21. Jun 1, 2005 #20
    [quote-monique]AND you must know that neutrophil cells of the immune system use respiratory burst to generate a large quantity of free radicals. These are packed in granules and released to the outside of the cell to kill bacteria.[/quote]
    What you nmean ? :confused: do you think you are trying toi be correctly stating it or just kind of metaphor explaning how atigen antibody tcell.in action ?

    by the way, i think saying ATP synthesis is driven by proton sound really strange, this stuff must be in enzyme instead.
     
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