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Chlorophyll Catalysis and Einstein's Law of Photochemical Equivalence in Photosynthesis

Otto Warburg, Gunter Krippahl and Arnold Lehman
American Journal of Botany
Vol. 56, No. 9 (Oct., 1969), pp. 961-971
Stable URL: http://www.jstor.org/stable/2440917
Page Count: 11
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Since scans are not currently available to screen readers, please contact JSTOR User Support for access. We'll provide a PDF copy for your screen reader.
Chlorophyll Catalysis and Einstein's Law of Photochemical Equivalence in Photosynthesis
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Abstract

We describe the catalysis of photosynthesis by chlorophyll: (a) chlorophyll bound to carbonic acid (that is, the photolyte) absorbs 1 quantum of light and is thereupon split into oxygen, reduced carbonic acid, and free chlorophyll; (b) the photolyte (that is, chlorophyll bound to carbonic acid) is resynthesized from carbonic acid and free chlorophyll with the help of the energy derived from the reoxidation of two-thirds of the reduced carbon formed in the light reaction. For calculation of the true quantum requirement of photosynthesis from experimental measurements, it is necessary to measure the light absorbed by the photolyte only, since the light energy absorbed by free chlorophyll is not used in the oxygen development of photosynthesis. To eliminate the loss of the light absorbed by the free chlorophyll, the factor ε = photolyte/total chlorophyll must be introduced into the calculation. Failure to take ε into consideration has led to discrepancies of 1,000% between the quantum yields obtained in different laboratories. These discrepancies are now removed. The quantum requirement of the splitting of the photolyte is always 1.

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