Introduction for the Interaction of Light with Biological Molecules


This lesson describes the nature of light, the energy within photons and how this energy may be transferred to biological molecules. In addition, the beneficial and harmful methods for de-exciting molecules will be described.


At the completion of this lesson, students will be able to:

  • Describe the nature of photons as quanta or packets of energy
  • Predict the relative energy in a photon from its wavelength
  • Describe the absorption process in terms of electronic state transitions
  • Describe four different pathways for de-excitation:
    • Fluorescence or thermal decay
    • Transfer of energy
    • Triple state conversion
    • Photochemistry
  • Differentiate between singlet and triplet electronic states
  • Understand photosensitization in terms of free radical generation of reactive oxygen
Peer Reviewed Web Lesson JNRLSE Approved 2003

Development of this lesson was supported in part by Cooperative State Research, Education, & Extension Service, U.S. Dept of Agriculture under Agreement Number 98-EATP-1-0403 administered by Cornell University and the American Distance Education Consortium (ADEC). Any opinions, findings, conclusions or recommendations expressed in this publication are those of the author(s) and do not necessarily reflect the view of the U.S. Department of Agriculture. This manuscript has been assigned Journal Series NO. 03-8, College of Agricultural Sciences and natural Resources, University of Nebraska.