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Photosystem I



The photosystem that makes use of light to transfer electron particualrly from plastocyanin to ferredoxin, and whose reaction center chlorophyll is P700.


Photosystem I is named I because it is first discovered before photosystem II. In fact, in plants and algae where two photosystems exist, the flow of electron begins at photosystem II.

Compared with photosystem II, the photosystem I is more complex in structure. It has a more complex antenna system, has more subunits in its overall structure, and may exhibit cyclic or non-cyclic electron transfer from the excited P700 to the electron acceptor.

Abbreviation: PS I

Compare: photosystem II

See also: P700

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I just taught that course (gr 12 photosynthesis): It appears that it is probably extremely unclear. I think it uses 4 photons per photosystem for each H2O broken. But since you need a mix of cyclic and non cyclic light reactions to produce anough ATP and NADPH, and that the cyclic reactions ...

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by canalon
Sat Apr 14, 2012 6:23 pm
Forum: Physiology
Topic: Photosynthesis
Replies: 2
Views: 3948


Is this statement true? Photosystem II is at highe energy level than Photosystem I.

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by chiayen
Sun Jan 15, 2012 4:43 am
Forum: General Discussion
Topic: photosystems
Replies: 1
Views: 1088

reverse photosynthesis and get respiration

... respiration (as mith said) think how mitochondrias work ( the thylakloid membranes and ETC's and then the chemeoosmosis) and compare that with photosystem... an abvious answer it is a big NO... and the reasons you can get even by thinking a little good luck thinking ;) thhough if you still ...

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by jwalin
Sun Apr 11, 2010 11:55 am
Forum: Cell Biology
Topic: reverse photosynthesis and get respiration
Replies: 8
Views: 5044

Re: Why do intact chloroplasts fluoresce?

... acceptor. So at what point is energy released as light? Thanks for your reply. Don't they drop back down to near the ground state when going from Photosystem II to Photosystem I? Would that cause the fluorescence in intact photosystems?

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by mamoru
Tue Mar 09, 2010 12:32 am
Forum: Botany Discussion
Topic: Why do intact chloroplasts fluoresce?
Replies: 10
Views: 8675

Biology IQ test: How smart are you = look

... electron sink in respiration. 15) RUBISCO is optimally evolved to work in an oxygen atmosphere. 16) The chlorophyll A molecules of the two photosystems are chemically different which causes their difference in absorbance spectra. 17) The large +G of life (all life collectively) is ultimately ...

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by DemiMike
Sat Nov 28, 2009 6:21 am
Forum: General Discussion
Topic: Biology IQ test: How smart are you = look
Replies: 3
Views: 13935
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