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Red blood cell general concepts.

  1. Feb 7, 2005 #1
    Can anyone correct me if im wrong? This is basic basic basic basic basic basic biology, and i am just trying to refresh my memory and make sure that i am stating the correct facts

    1) General concepts about tonicity
    Lets say for example, we have a red blood cell exposed to solutions of different tonicity (hypo, iso, hyper)

    If the red blood cell was hypotonic to the solution, then the red's blood cell volume will increase, and ultimatey lysing the cell.

    If the red blood cell was iso to the solution, it will make no differenfce

    If the red blood cell was hyper to the solution, the cell would shrivel as water will leave the cell and thus losing volume in the red blood cell.

    2) Lets say for example, the isotonic concentrations for the red blood cell's was exposed to different solution of increasing osmlarity but equal concnetration. If this was to happen, osmosis would be in equilibrium, since osmosis is only determnined only by a difference in total solute concentration, nut just spefically different solutions.

    3) If polar molecules of increasing molecular weight was introduced to the red blood cell plasma membrane, then how would the rate of transport across the red blood cell membrane change? Well, first of all , it is very hard for a polar molecule to pass thru the membrane, let alone the size. So, the rate of transport across the red blood cell membrane would greatly be reduced.

    So am i stating the correct facts. Or are they any more stuff that can be added to my concepts? If im wrong anywhere, can you show me where and why?

  2. jcsd
  3. Feb 7, 2005 #2


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    There are some errors, so I'll try to offer some hints for you to find them yourself (you'll remember it better if you find your own mistakes).
    1) You're saying the (contents of the) red cell are hypo- or hypertonic relative to the solution it is in. What does that mean in terms of ion concentration inside the cell, and outside the cell (outside=solution)? Be careful whether you are referring to the contents of the cell as hypo/hypertonic, or the solution as hypo/hypertonic relative to the other.

    2) What is the definition of osmolarity? What is the definition of concentration?
  4. Feb 8, 2005 #3
    i see...

    for 1) i should have said the solution "..." to the cell instead of the other way around.

    for 2) osmorality is defined as solute concentration defined as molarity (moles of solute/liters). What exactly is concentration?? Ahh sorry for asking such a stupid question....

    and i am totally clueless on how different solutes at the same concentration cuold hvae different osmolarities

    also for 3)..is my conceptual thinking right on this part?

  5. Feb 8, 2005 #4


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    That's why I asked you to define both osmolarity and concentration. Osmolarity (molarity) is a measure of concentration. That part of the question made no sense to me, unless you're attempting to use two different measures of concentration. For example, if you are talking about two different solutes, then the solutions made from them could have the same osmolarity, but concentration as measure in g/mL would be different because that would depend on the molecular weight. But, in terms of diffusion, weight/volume measures of concentration aren't relevant, it's molarity that matters.

    As long as you're talking about the ability of molecules of different sizes to diffuse into a cell (it wasn't completely clear from the wording of the question). From the general trend of the questions, I assume they are all referring to simple diffusion.
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