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Homework Help: Estimation of number of Carbon atoms in bacterium

  1. Sep 8, 2010 #1
    1. The problem statement, all variables and given/known data
    Minimal growth medium for bacteria such as E. coli includes various salts with characteristic concentrations of mM and carbon source. This carbon source is typically glucose and it is used at 0.2% ( a concentration of 0.2g/100mL).

    a) Make an estimate of the number of carbon atoms it takes to make up the macromolecular contents of a bacterium such as E. coli.

    b) How many cells can be grown in a 5 mL culture using minimal medium before the medium exhausts the carbon?

    2. Relevant equations
    Molar mass, Avagadro's number

    3. The attempt at a solution
    I first started out by taking the concentration of .2g/100mL and figured out the mol of glucose per 100mL. Then I found mol of carbon and through Avagadro's number, I found the number of atoms per 100mL. Is this the right method?

    I also thought of finding the volume of glucose molecules and dividing the volumes to find the amount of glucose molecules in the bacterium and finding the number of carbon atoms through that?
  2. jcsd
  3. Sep 9, 2010 #2


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    Staff: Mentor

    Either I am missing something completely, or you have to find some additional data to solve the question.

    Using volumes of a single E. coli and glucose molecule is not a completely bad idea, but - as most of the bacterium is water - it will give incorrect result. But at least you will know what order of magnitude we are talking.
    Last edited by a moderator: Aug 13, 2013
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