Electron Transport by Diffusible Molecules

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  • R. P. F. Gregory
Part of the Tertiary Level Biology book series (TLB)


In green plants, the slowest part of photosynthesis was detected by an experiment performed by Emerson and Arnold in 1932 in which leaves or cells were illuminated by a succession of very short flashes. It was found that the maximum rate of oxygen production or carbon dioxide uptake could be obtained with repetition rates of 100 per second, even though, with a flash duration of 10 µs, the plant was only receiving light for 1/1000 of the time. The slowest step was (much later) traced to the reduction of a C-type cytochrome, cytochrome f, by the plastoquinol formed by PSII. Cytochromes are relatively easy to observe since their sharp α-bands in the reduced state can be measured spectroscopically in the window between the blue- and red-absorbing peaks of the chlorophyll. Cytochrome f in the reduced state has its α-band at 554.5 nm.


Electron Transport Photosynthetic Electron Transport Hydrogen Sulphide Purple Bacterium Green Sulphur Bacterium 
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Further reading

  1. Hauska, G. (1986) Composition and structure of cytochrome bc 1 and b 6 f complexes. In Staehelin, L.A. and Arntzen, C.J., eds., Photosynthesis III. Photosynthetic membranes and light harvesting systems. Encycl. of Plant Physiol. new series, Vol. 19, Springer-Verlag, Berlin, 496–507.Google Scholar
  2. O’Keefe, D.P. (1988) Structure and function of the chloroplast cytochrome bf complex. Photosynthesis Res. 17, 189–216.CrossRefGoogle Scholar

Cited references

  1. Anderson, J.M. (1987) Molecular organisation of thylakoid membranes. In Amesz, J., ed., Photosynthesis. New Comprehensive Biochemistry Vol. 15 Elsevier Amsterdam, 273–297.Google Scholar
  2. Barber, J. (1984) Further evidence for the ancestry of cytochrome b-c complexes. Trends Biochem. Sci. 9, 209–211.CrossRefGoogle Scholar
  3. Mitchell, P. (1976) Possible molecular mechanisms of the protonmotive function of cytochrome systems. J. Theor. Biol. 62, 327–367.PubMedCrossRefGoogle Scholar
  4. Pschorn, R., Rühle, W. and Wild, A. (1988) Structure and function of ferredoxin-NADP+-oxidoreductase. Photosynthesis Res. 17, 217–229.CrossRefGoogle Scholar

Copyright information

© Blackie and Son Ltd 1989

Authors and Affiliations

  • R. P. F. Gregory
    • 1
  1. 1.University of ManchesterUK

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