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Homework Help: Chromosome damage

  1. Feb 1, 2009 #1
    Somebody tells you that a single ultraviolet photon carries an energy equivalent of about 10
    electron volts (eV, see Appendix B). You propose a damage mechanism: A photon delivers that
    energy into a volume the size of the cell nucleus and heats it up; then the increased thermal
    motion knocks the chromosomes apart in some way. Is this a reasonable proposal? Why or why

    (Heat produced) = (mechanical energy input) * (0.24 cal/J)

    so that

    Heat produced = 3.84E-19 cal
  2. jcsd
  3. Feb 1, 2009 #2


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    That's a good first step. Now you need to convert that energy into a change in temperature. To do this, you need to find the mass of a typical cell nucleus by finding the volume and assuming it has the same density as water (typically a good assumption when working with cells).
  4. Feb 1, 2009 #3
    Assuming a cell nucleus diameter of ca 2 micrometers and mass density equal to that of water, the mass of the nucleus is 4E-15 kg.

    I'm not sure how to calculate the temperature rise. Can I simply use

    \Delta E_k = \frac{3}{2} k_B \Delta T

    as for gases?
    Last edited: Feb 1, 2009
  5. Feb 1, 2009 #4


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    You'd have to use the more general formula

    q = mcΔT

    Where q is the amount of heat transfered, m is the mass, c is the specific heat capacity, and ΔT is the change in temperature.
  6. Feb 1, 2009 #5
    Should I assume the same specific heat capacity as water too?
  7. Feb 1, 2009 #6


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