Is Chromosome Damage Caused by Ultraviolet Photons a Reasonable Proposal?

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Discussion Overview

The discussion revolves around the proposal that ultraviolet photons can cause chromosome damage through a thermal mechanism. Participants explore the energy carried by a single ultraviolet photon and its potential effects on the cell nucleus, focusing on the calculations involved in determining temperature changes resulting from this energy input.

Discussion Character

  • Exploratory
  • Technical explanation
  • Mathematical reasoning

Main Points Raised

  • One participant proposes a mechanism where the energy from a single ultraviolet photon heats the cell nucleus, potentially leading to chromosome damage.
  • Another participant suggests calculating the temperature change by first determining the mass of the cell nucleus, assuming it has the same density as water.
  • A participant calculates the mass of a typical cell nucleus and questions whether the kinetic energy formula for gases can be applied to find the temperature rise.
  • Another participant recommends using the general heat transfer formula, indicating the need for specific heat capacity in the calculations.
  • A participant inquires if the specific heat capacity of water should be assumed for the calculations.
  • Another participant confirms that assuming the specific heat capacity of water is appropriate.

Areas of Agreement / Disagreement

Participants generally agree on the approach to calculating the temperature change and the assumptions regarding the density and specific heat capacity of water. However, the initial proposal regarding the mechanism of chromosome damage remains a topic of exploration without explicit consensus.

Contextual Notes

Limitations include assumptions about the density of the cell nucleus and the applicability of the kinetic energy formula for gases to this context. The specific heat capacity assumption may also depend on the biological context of the cell nucleus.

Who May Find This Useful

This discussion may be useful for those interested in the effects of ultraviolet radiation on biological systems, particularly in the context of cellular damage and thermal dynamics.

kasse
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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
not?


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

so that

Heat produced = 3.84E-19 cal
 
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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).
 
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

[tex] \Delta E_k = \frac{3}{2} k_B \Delta T[/tex]

as for gases?
 
Last edited:
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.
 
Should I assume the same specific heat capacity as water too?
 

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