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Thread: Microbiology: Osmolarity help!

  1. #1 Microbiology: Osmolarity help! 
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    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 Masters Degree mat5592's Avatar
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    The cells should, in theory, swell, as water would rush in. Maybe look for some other variables that seem to be preventing this.

    Edit: I see you got a much more thorough answer in the chemistry forum


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  4. #3  
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    Theoretically, the lysozyme should have degraded the peptidoglycan walls until their effect, on maintaining cell structure and stopping it from bursting, was removed.
    I can never know I'm right, but I can know that I'm wrong.
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    Forum Junior AndresKiani's Avatar
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    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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    No more double threads btw Hogmann :P
    I can never know I'm right, but I can know that I'm wrong.
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  7. #6  
    Forum Junior AndresKiani's Avatar
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    Quote Originally Posted by Curiosity View Post
    Theoretically, the lysozyme should have degraded the peptidoglycan walls until their effect, on maintaining cell structure and stopping it from bursting, was removed.
    Yeah I thought so too. What would happen is that when the Bacterium gets engulfed via COP proteins. The Bacterium's cell wall proteins should denature chemically speaking as fusing vesicles transfer it to the late endosomes. The pH starts dropping even in the late endosomes before it gets to the lysosome. Once it gets to the lysosome most of it should have already been broken down, not to mention that many lysosomal enzymes cleave the sugars that hold together the peptidoglycan walls. Thus it will degrade and get broken down inside the lysosome.

    Also the lysosome is not a storage, it will use exocytotic bound vesicles to get rid of the junk that the cell won't use, and other vesicles will bud off from the lysosome storing the monomers that the cell will use.

    The lysosome from my knowledge will not have a significant K+ or other ion concentration. Lysosomes are usually highly concentrated with H+ protons, thanks to their atpases (V-ATPase family) that constantly keeps these protons inside the lysosome. Keeping it highly acidic.
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