Can someone please help explain to me what cyclic e- flow is in photosynthesis?

[Vsno123]

Ok so I have been searching for an hour now and I can't seem to figure out what cyclic e- flow is in photosynthesis? Everywhere I go (even my old bio textbooks) seem to focus more on noncyclic.

From what I gathered researching on the internet, cyclic e- flow is a result of the Calvin Benson cycle needing more ATP than it does NADPH (especially if there is too much NADPH present and there is no NADP+ to accept the e-).

How much ATP and NADPH is needed to propel the Calvin cycle? Also, I keep seeing that the cyclic electron flow only involves PS1 but then it uses the ETC of PS2 to generate ATP via chemiosomosis? And then something about ferrodoxin?

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[LetsGo2DSchool]

It's explained well enough in Cliffs AP bio. If you do a Google image search, you should be able to find some diagrams that are self-explanatory.

Whatever you do, don't use Kaplan's explanation as their ******ed unconventional method of teaching it totally f**ks it up and will confuse you further.

 

[LetsGo2DSchool]

Alright, I did a quick image search and there aren't too many good diagrams. So here it is in a nutshell...

Light hits Photosystem I and eventually shoots an electron up to a primary electron acceptor. Most of the electrons at this point enter noncyclic flow to join with NADP+ to become NADPH before it enters Calvin Cycle. Some electrons enter a cyclic flow instead, making ATP in the process, before it goes back to Photosystem I and then repeats the process again (gets shoot up to a primary electron acceptor and so on).

In the below diagram, the path of the purple boxes is cyclic flow.

View attachment cyclic.jpg

 

[LetsGo2DSchool]

duplicate post

 

[Vsno123]

Yeah, in the Kaplan BB there's only a paragraph, I think, on all of photosynthesis! I have Barron's AP but it's pretty basic. I'm just going to go with it and stop stressing over one little detail. Thanks for the help!

 

[UCLAzy]

you should understand that cyclic and non-cyclic flow occur at the same time. obviously in non-cyclic flow if the electrons go that way they wont get recycled, but electrons that do cyclic flow might get recycled a few times and then go to non-cyclic. this is something i struggled to understand..as i initially believed that cyclic electrons ONLY did the cyclic ATP generation and didnt do non-cyclic..if that makes any sense whatsoever

 

[Bis-GMA111]

light-->captured in PSI-->electrons excited-->back to PSI (when going back to PSI ATP is produced)

 

[DrRoyal Pains]

Like PreDENT1210 said, the electrons are not incorporated into the Calvin Cycle. They go back through the ETC between PS II and PS I and will synthesize addtional ATP.

 

[invictusx]

Ok so I have been searching for an hour now and I can't seem to figure out what cyclic e- flow is in photosynthesis? Everywhere I go (even my old bio textbooks) seem to focus more on noncyclic.

From what I gathered researching on the internet, cyclic e- flow is a result of the Calvin Benson cycle needing more ATP than it does NADPH (especially if there is too much NADPH present and there is no NADP+ to accept the e-).

How much ATP and NADPH is needed to propel the Calvin cycle? Also, I keep seeing that the cyclic electron flow only involves PS1 but then it uses the ETC of PS2 to generate ATP via chemiosomosis? And then something about ferrodoxin?

Ferrodoxin is an iron-sulfur protein that facilitates electron transfers because the irons can easily be oxidized and reduced.