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Homework Help: Diffusion or osmosis?

  1. Nov 22, 2015 #1
    1. The problem statement, all variables and given/known data
    Is the oxygen required by the single-celled organisms obtained by diffusion or osmosis through the surface membrane of the cell?

    2. Relevant equations

    3. The attempt at a solution
    I'm thinking osmosis since there's a membrane through which the oxygen passes. But I've been looking at definitions of osmosis and some talk of osmosis is only to do with water moving from high to low concentration. Diffusion is about any molecule moving anywhere.

    Bit confused. Please advise. Thank you
  2. jcsd
  3. Nov 22, 2015 #2
    You are right
    Diffusion is in all states of substances
    Osmosis is usually confined to solutions ;)
  4. Nov 22, 2015 #3
    The book I'm reading said oxygen required by the single-celled organisms diffuses across the surface membrane of the cell? I wasn't convinced that was accurate because there's a membrane involved so must be osmosis. But definitions I read about osmosis talk only of osmosis of water across a membrane. But I'm talking of oxygen (not water) so it :
    "osmosis of oxygen (NOTE : no need to mention the word membrane because it is assumed a membrane exists in osmosis)" or "diffusion of oxygen across a membrane".
  5. Nov 22, 2015 #4


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    Osmosis is a term that refers exclusively to the diffusion of solvent molecules (in most cases, water) across a semi-permeable membrane. The spontaneous crossing of all other substances across a membrane would be referred to as diffusion.
  6. Nov 22, 2015 #5
    Thanks. Thats cleared by confusion. Osmosis is the diffusion of the liquid molecules across a membrane (in the body it would be water but in chemistry could be anything e.g an alcohol) in which the substrate (in this case oxygen) is dissolved. The substrate diffuses across the membrane
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