|WikiProject Molecular and Cell Biology||(Rated C-class, High-importance)|
photophosphorylation = Light-dependent reaction?
For some reason, the photophosphorylation article is re-directed into Light-dependent reaction article. The two, in my opinion are not the same and therefore shouldn't be linked. The former is more tightly related to plants, while the later can in fact be applied even to photovoltaic cells (solar cells)
- It would be a good idea to expand the Light-dependent reaction article to include non-biological examples of this, but keep the redirect (as otherwise it would just be duplication of content). Or perhaps it would be better to turn the light-dependent reaction page into a disambiguation page. Thoughts? Talrias 10:35, Feb 5, 2005 (UTC)
- Photovoltaic cells do not phosphorylate anything. There's more to the light reactions than photophosphorylation, but the redirect seems appropriate to me. dsws 02:27, 12 July 2005 (UTC)
Is NADPH considered as stored energy?
Just wondering , because all the sources I found so far states that it is just a reducing agent (but it did not say it's not an energy store). But isn't it also chemical energy then?
---NADPH is also an energy storing molecule, yes.
---It is a reducing agent; however, it has a rather highly negative reduction potential -- that is to say, its oxidation is very thermodynamically downhill. Therefore, NADPH can transfer electrons to chemicals that are not normally easy to reduce. This includes CO2 in the Calvin-Benson cycle. It also explains how so much energy becomes available to pump protons to mitochondrial ETC reactions where the reducing power of NADH is coupled to many uphill reactions. —Preceding unsigned comment added by 18.104.22.168 (talk) 02:18, 14 December 2009 (UTC)
curious as to why it says "SENS RULE!!" after number 7 in the steps section... it could be vandalism considering i've never heard of any such thing and i doubt it has anything to do with the calvin-benson cycle.Annie 02:23, 27 November 2006 (UTC)
--- it was vandalism, so i removed it.
I think this discription contains a mistake stating: "passes from the primary acceptor to ferredoxin, then to a complex of two cytochromes (similar to those found in mitochondria), and then to plastoquinone before returning to chlorophyll". It is supposed to be plastocyanin that carries the electrons back to the PS1, isn't it?
- jeah, you are totally right. Ferredoxin can't gives electons to cytochrome b6f. I fixed it. (Kasper90 (talk) 01:03, 4 January 2009 (UTC))
The first figure (https://en.wikipedia.org/wiki/Light-dependent_reactions#/media/File:Thylakoid_membrane_3.svg) and accompanying description do not clearly show how the electrons are recycled so as to avoid the production of NADPH. This cyclic process is shown later on, but in less detail, in the animated figure (https://en.wikipedia.org/wiki/Light-dependent_reactions#/media/File:Light_Dependent_Cyclic_Reactions.gif). I lack the graphic arts skill to fix this myself, but if I am right, someone should change the figure and accompanying text to make the cyclic path clear, e.g. by adding a blue dotted arrow to represent electrons returning from PSI to PSII.CharlesHBennett (talk) 13:15, 19 January 2017 (UTC)
ET in photosynthesis is solid-state?
There appears to be a comment in this page that suggests electron-transfer in photosystem II should be considered a solid-state reaction. I vehemently disagree with this statement; however, I figured it would be more appropriate to bring it up in discussion rather than change it on my own. The contributor seems to think that because the protein arranges a crystalline state, it cannot be considered a chemical reaction. He/she goes further to say that chemistry is described by "random energy distributions." Both claims seem to me do be false. Yes, proteins pre-organize highly specific architecture, however that is entirely in the purview of supramolecular chemistry. If pre-organized architecture was equivalent to the solid-state, then every protein-mediated ET would need to be considered "solid-state," which makes a mockery of the long tradition of chemists who have studied ET in proteins through the molecular framework, and have used it both to understand results and predict phenomena. The solid-state facilitates electron transfer not simply because of rigid structure, but rather, because the solution to Schrödinger's Equation for a periodic potential reduces to Bloch waves, which reveals that the state in position space is unlocal and reduces to a Fermi gas. A protein might be rigid, but it is by no means macroscopically periodic. The efficiency of ET is a testament of supramolecular functionality. It looks like a solid-state physicist has sour grapes over photosynthesis. 22.214.171.124 (talk) 02:31, 14 December 2009 (UTC)
I understand that many have emotional comments about this article. I studied photsynthesis at UCB with Melvin Calvin (who described the first enzyme in the Calvin Cycle-RUDP carboxylase for which he earned a Nobel Prize) and Daniel Arnon who discovered photophosphorylation. This page needs to be edited and I can do it.
I also worked with Bob Buchanan at UCB who is a world expert on the dark reactions of photosysnthesis. I am credited with describing the first allosteric (regulatory) enzyme in the Calvin Cycle: Sedoheptulose 1,7 Bisphosphatase.
The article starts with: The light-dependent reactions, or photoreduction, is the first stage.... Are the light-dependent reactions really called 'photoreduction'? One type of what the literature calls 'photoreduction' is the light-stimulated reduction of Mn(IV) to Mn(II) in for instance the euphotic zone of seawater. This process is unrelated to photosynthesis.
I suggest that we either remove the term 'photoreduction' as a substitute for 'light-dependent reactions', or please back up the usage with citations (if in doubt, put them here in the discussion). Hulten (talk) 12:19, 5 June 2014 (UTC)