Electron flow in photosynthesis

John Bohmfalk jbohmfal at hastings.edu
Mon Apr 26 14:19:13 EST 1999

To all:

I have also posted this to the biolab group.  For those of you who
subscribe to both, I apologize for the duplication.

In virtually all discriptions of electron flow in photosynthesis both
non-cyclic electron flow (generating both ATP and NADPH) and cyclic
electron flow (generating only ATP) are described.  My questions concern
the regulation of the two processes.

Do both occur simultaneously in a chloroplast so that the net production of
ATP is greater than NADPH?  Or, is non-cyclic flow regulated so that if the
relative concentration of NADPH is sufficiently high relative to ATP, that
process is inhibited so that non-cyclic will occur for a while? OR, is
cyclic flow inhibited by sufficient ATP so that the non-cyclic flow is the

What gives here?

Thanks greatly.


John F. Bohmfalk                                        jbohmfal at hastings.edu
Associate Professor of Biology                          (402) 461-7470
Biology Department                                      FAX:  (402) 461-7463
Hastings College
Hastings, NE  68901

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