I know that NADP+ gets reduced to form NADPH, but what exactly is being donated? Is it two individual electrons (from photolysis or the chlorophyll molecules) and a hydrogen ion (proton)? If this is the case, during the Calvin Cycle, do the NADPH molecules donate the same two individual electrons and hydrogen proton from the light-dependent reactions to become NADP+ again? Thanks.

  • $\begingroup$ SE Biology expects you to show what research you have done to answer this question (the title of which should be repeated in its body). Just googling for "non-cyclic photophosphorylation" gives the answer to your title in a callout box at the top of the page. $\endgroup$ – David Jan 23 '18 at 9:33

Specifically during non-cyclic photophosphorylation, I know that the chlorophyll already has preexisting NADP+ molecules, water is broken to release 2 hydrogen atoms and 1 oxygen atom (two water molecules break down to form gaseous oxygen that we breath), those 2 hydrogen atoms get sent down and along the Electron Transport Chain via solar energy and then I believe one goes to a protein called ATP synthase and the other goes to photostem 1. After photostem 1 that hydrogen binds to free floating NADP+ molecules to from charged NADPH. This should be the gist of it all but I would also recommend listening to someone else's input as well.

  • $\begingroup$ Wait, I thought that photolysis splits water into two electrons, 1/2 of O2, and two hydrogen ions which are just protons. I'm pretty sure the hydrogen ions contribute to the H+ concentration, not to the photosystems because that's where only the electrons go in which they ultimately end up reducing NADP+ $\endgroup$ – Ricky Zhang Jan 23 '18 at 0:28
  • $\begingroup$ Okay, I've done some research and yes thank you, that was the part that I was forgetting. The positive hydrogen ions go through the ATP synthase while the electrons follow the ETC, after phyotosystem 1, I believe those electrons will diffuse because they repel while the hydrogen ions are also repelling each other (keep in mind they are both outside of the thylakoid membrane now). This I believe results in the electrons and hydrogen's coming back together to later be randomly paired up with NADP+ molecules. $\endgroup$ – X9Z3 Jan 23 '18 at 0:52
  • $\begingroup$ At SE Biology we're looking for answers that provide some explanation and context. Explain why your answer is right, using citations. How is the poster to be able to check whether your answer is correct? $\endgroup$ – David Jan 23 '18 at 9:35
  • $\begingroup$ First, "I believe" is what shows your lack of effort to give a nice answer. Second, the OP themselves stating that you give wrong information in your answer is exactly what is not expected from answers on SE (or at least Biology.SE). Please show some research effort for an answer (this is probably the first time I have said this here) $\endgroup$ – another 'Homo sapien' Jan 23 '18 at 12:28
  • 1
    $\begingroup$ Thank you @another 'Homo sapien' and David, I'm sorry for the lack of effort. $\endgroup$ – X9Z3 Jan 26 '18 at 8:32

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