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Thread: Microbiology: Osmolarity help!

  1. #1 Microbiology: Osmolarity help! 
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    Sep 2014
    I am working on a microbiology lab write up and can't seem to figure out how KCl would effect a certain trial for a Gram positive bacterium cell when lysozymes were added. I understand that the lysozymes cut the peptidoglycan of the Gram positive cell. If the certain cell has an osmolarity of around 800 mOsm and the KCl makes the solution approximately 450 mOsm would the water rush in, out, or stay the same (hypotonic, hypertonic, isotonic)? My cells did not burst but I assumed they should have?

    Thanks for your help

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  3. #2  
    Forum Junior AndresKiani's Avatar
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    Jan 2014
    Never took Microbiology, but..

    To answer your question however, if 800 mili moles inside the cell, and 450 mili moles concentration outside the cell. This should mean that the osmotic flow would favor the inside of the cell. Therefore the solution is hypotonic, and will burst the cell theoretically.

    However, the peptidoglycan complex of its' cell wall may have given some of those bacterium some tonacity to keep from bursting. I've never taken Microbiology, so I do not know if Bacterium have large vacuoles or any sort of turgor force that may push back. Answer is who knows.. lol.

    I guess in chemistry we do.. calculate osmotic pressure, I've done this in lab for none living systems.

    TT = iMRT
    TT - in torr (1 torr = 760 mmHg)
    I - # particles
    M - Molarity of KCl
    R - 0.08206
    T- temp. in kelvins...

    Maybe you can take the difference in pressure, to see how net pressure is exerted on the cell wall.

    TT = 2(MolarityKClsolution inside cell)0.08206(solution Temp.) - 2(MolarityKClsolution outside cell)0.08206(solution Temp.)

    That might give you a basic idea of how much force is being exerted on the cell wall.

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