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Medical What is life?

  1. Feb 28, 2017 #1
    Thereis no proof for anything in us other than matter(and energy).
    Thermodynamics works everywhere.
    I think we live upto the time our system's Delta G (Gibbs free enery) remains negative.
    Please friends tell me if my undrstanding is justified.
     
  2. jcsd
  3. Feb 28, 2017 #2
    I don't see that as making a lot of sense.
    For example many people die because of some kind of cancer.
    Some people respond well to therapy and can completely recover, others don't.
    There is a lot more to it than a purely thermodynamic situation equivalent to something like an engine running out of fuel.
     
  4. Feb 28, 2017 #3

    Drakkith

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    What is life? Wikipedia's article gives a good overview of what our current views are: https://en.wikipedia.org/wiki/Life

    Thermodynamics is certainly useful to understand how various aspects of biology work, most notably the chemical reactions that occur inside your cells, but the laws of thermodynamics don't do anything other than explain how heat and energy work. The idea that we only live while our ΔG is negative is not very useful. You might as well say that we only live until our cells run out of fuel. While true, all the details and complexity are lost.
     
  5. Feb 28, 2017 #4
    Still I do not understand any underlying thing other than Physics about life.What else is there except delta G negative .We are an outcome of a number of reactions and through coupling net delta G remains negative I think.
    Anyway I will read article in link.Thanks!
     
  6. Feb 28, 2017 #5
    I think that trying to describe life as a simple equation is a lost cause.
    There are thousands of variables and few known constants.
     
  7. Feb 28, 2017 #6

    Drakkith

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    That's merely a single way of looking at it. I could boil everything down to fundamental forces, and it would be an equivalent way of looking at things.
     
  8. Mar 1, 2017 #7

    Fervent Freyja

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    Living matter is notably different than nonliving matter: It is the only system that uses gases, in combination with the intake of other forms of matter, such as water, sunlight, and nutrients in order to move around, intentionally (goal-directed). It's this unique and incredibly complex system that prevents us from being able to describe it in the ways that we can nonliving matter at the molecular levels, such as a rock.

    On the topic of thermodynamics, lifeforms are semi-closed (open) systems- which is good, as that allows for metabolism, respiration, and reproduction. Those laws apply to isolated systems. I do think, however, that when we look at smaller cellular levels such as DNA, we do see that the system is more closed compared to the overall lifeform, as genetic information has been passed for millions (billions) of years- the addition and changes of genetic information can be loosely interpreted as an increase in entropy of the system. Lifeforms that we see today, including ourselves, are each essentially a container that has been passed down through reproduction for a very long time- we are far older than we give ourselves credit for. We are all a continuum of a small system that began long ago, life has only emerged once. Nonliving matter cannot touch the beauty of the ongoing process of life.
     
  9. Mar 1, 2017 #8
    I think science of today is simply not enough to know what is life. We don't have to feel ashamed about it. Our endeavor is to achieve complete knowledge. But we have not reached there, yet.
     
  10. Mar 1, 2017 #9
    Dynamics gianeswhar. That's what else. To understand life, I believe we must remove the inconsequential trappings of biochemistry and even thermodynamics and look purely at the underlying dynamics. But to do so, it takes a life-time of studying differential equations. It is there we find the secrets to the Universe. If you write all the equations of mathematical physics on strips of paper and toss them to the kitchen floor, they won't get up and dance but if the strips behaved in a sufficiently complex (non-linear) fashion, surely they would. In this view, it is not chemistry, physics or even thermodynamics that gives life to life but rather pure dynamics that happens to be instantiated in biology on earth. Silicon would do. Marbles too.

    And as an example of this view, consider the Brusselator. This is a coupled system of non-linear PDEs. And the fascinating thing about this system is that we can set it up in a random state, and evolve the equations in time, and under certain conditions, just by the purely underlying dynamics, order in the form of dots and spirals and other patterns (like a leopard) emerge. Consider termite mounds, the marvelous clay cathedrals they build is not by some master plan but rather through non-linear interaction of pheromone, mud and termite. This has been experimentally verified (also using coupled PDEs). See "Self-organization in Biological Systems" by Camazine. Again, it is the underlying dynamics that gives rise to complex structures and it is not an inappropriate stretch of reasoning in my opinion to suggest there exists immensely complicated equations that we do not yet know that would do the same for the origin and evolution of life on earth.
     
    Last edited: Mar 1, 2017
  11. Mar 1, 2017 #10
    Thank you very much aheight for your excellent openion.I will take some time to understand and respond.
     
  12. Mar 1, 2017 #11

    Fervent Freyja

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    No, that statement is not enough, like Drakkith already wrote. While true, it's the equivalent of me saying: If I stop breathing then I die. We could form true statements about what life is all day long. It does not offer us any more information about the system until we apply it and form quantitative models. While applying principles of non-equilibrium thermodynamics has helped describe a few cellular biological process, such as protein folding and membrane transport, it hasn't been successfully applied to completely describe a large living system outside the cellular levels. Can you use it to totally predict behaviors or explain the molecular complexity of any lifeform? No.

    I would not call life an "accident" if you believe in determinism, a better statement would be that life is an outcome. Even now, what constitutes a system to be a lifeform is still disputed in science.

    I agree that there may be no 'subtle forces at work' and lifeforms should be describable more precisely with physics one day. But that is only to a certain point, even a GUT that offered a satisfying description would not shake the faith of most humans alive today. I doubt we could ever fully answer the big questions: What is life? Why do we exist? Humans can always retain their faiths. Even if that isn't for me, I can respect their preferences.

    I also have a more mechanical perspective of life, but it enhances the beauty of it for me. You do not believe that the mechanical complexity around you, the outcome of what you are, is beautiful? The complexity of the three young humans before me at this very moment rivals larger bodies such as the moon. They are requesting their energy needs be met- "get off your computer and feed us breakfast, so we can expend energy on the playground later". Nonliving matter does not behave that way!

    Some reading on biological thermodynamics: https://arxiv.org/pdf/physics/0012036.pdf
    https://ocw.mit.edu/courses/biologi...biomolecular-systems-fall-2005/lecture-notes/
    http://home.iitk.ac.in/~osegu/NonEquilThermo.pdf
     
  13. Mar 1, 2017 #12
    'Life' might be hard to define, but fortunately there is already a precedent for such problematic matters: the good old 'I know it when I see it' standard.
    If one wants to apply it on advanced level, then can say: I know it when it bites me'. That will cover it just finely.
     
  14. Mar 1, 2017 #13
    Thank you all friends and especially Ferventt Frejya for like you provided.Iwill take some time to study these.
    Fervent! You seem to put some thing other than Physics in life......like beauty...
    I believe beauty of anything is also a trick of brain in pleasure centre etc ...or may be some chemical process like release of dopamine...seretonine...etc.
     
  15. Mar 1, 2017 #14

    Drakkith

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    Thread locked for moderation.
     
  16. Mar 1, 2017 #15

    Drakkith

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    This thread is an absolute mess. Nearly half the posts have been deleted for various rules violations.

    Thread will remain locked.
     
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