Lab 4: Plant Pigments and Photosynthesis

  1. In paper chromatography, how does the solvent move up the paper?
    attraction to the paper and solvent molecules to one another
  2. Why do the pigments travel at different rates?
    not equally soluble in the solvent and because they are attracted to different degrees to the fibers in the paper through the formation of intermolecular bonds.
  3. Which pigment migrated the farthest?
    beta carotene
  4. How do you find the Rf value?
    • Distance pigment migrated
    • Distance solvent front migrated
  5. What factors are involved in separation of the pigments?
    • solubility, size and attraction to the paper and cellulose of the paper forming bonds (H)
    • - not equally soluble in te solvent and are atracted to different degrees
  6. Would you expect the Rf vaule of a pigment to be the same if a different solvent were used? Explain.
    No because difernet pigments would have differnet solubilities and different attractions. It will change the migration distance and therefore Rf values.
  7. For studying photosynthesis, what chemical are we using?
    DPIP which is blue when oxidized and clear when reduced
  8. What wavelength must you first put the spectrophotometer to?
    605 nm
  9. What is the independent variable?
    • independent: time
    • dependent: absorbance/ transmittence
  10. If the graph for unboiled light is of absorbance, how should the graph look? transmittance?
    • absorbance going down
    • transmittance going up
  11. What is the purpose of DPIP in the experiment?
    It replaces NADPH as an electron acceptor and receives the electrons after they go down the second electron transport chain. When light is absorbed, it excites elecrons causing them to go through PSII and PSI and to DPIP, reducing it, turning it from blue to colorless.
  12. What does DPIP replace?
  13. What is the source of electrons that will reduce DPIP?
    water which releases O2, two protons and two electrons. THe two electrons fill the P680+ hole.
  14. What was measured with the spectrophotometer?
    it measures absorbance/ transmittance over a period of time. When DPIP is blue, it has a high absorbance rate and low transmittance rate. When it is colorless, it is opposite.
Card Set
Lab 4: Plant Pigments and Photosynthesis
AP Bio