Photosystem Question

[FrostyFlakes]

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This is a sample problem from Kaplan

The P680 chlorophyll A molecule of photosystem II:

A oxidizes glucose.
B oxidizes water.
C best absorbs light with a wavelength of 700nm.
D provides electrons that reduce NADH+.
E more than one of the above.




Answer is B according to Kaplan. But P680 PSII ultimately provides electrons for this whole thing to work by oxidizing water, so it is the ultimate source of electrons. Is that bad logic or bad question?

 

[Hope30]

Both are good logic and question. In photosystem II, H2O is broken down to H+ and O2; as a result, 2 e- is transferred to the chlorophyll, working like a domino in a way. The e- is excited. The H+ is later used in the ETC as a photon gradient, and O2 as e- acceptor making H2O again (I believe).

 

[FrostyFlakes]

Both are good logic and question. In photosystem II, H2O is broken down to H+ and O2; as a result, 2 e- is transferred to the chlorophyll, working like a domino in a way. The e- is excited. The H+ is later used in the ETC as a photon gradient, and O2 as e- acceptor making H2O again (I believe).

But doesn't PSI get its e- from PSII? Wouldn't that make choice D correct as well?

 

[crax]

But doesn't PSI get its e- from PSII? Wouldn't that make choice D correct as well?

i thought psI gets excited from absorbing the energy, but the electron isnt transferred. i may be wrong though

 

[flyingforever]

i thought psI gets excited from absorbing the energy, but the electron isnt transferred. i may be wrong though

Both Photosystems can absorb light energy and can transfer electrons. However, PSII absorbs better, read "quenching of fluoresce" if you want crazy details.