Answer:
-Photosynthesis can be divided into
light reaction and dark reaction.
Light reaction occurs in the grana of
chloroplast.Light reaction begins with the trapping light energy by chlorophyll
molecules of the photosystems.The energy absorbed by chlorophyll molecules in
PS 2 is channeled to P680,reaction center for PS 2.This causes P680 to be photoactivated,thus
PS 2 is photoactivated.The electrons in P680 become excited and escape from
P680.These electrons are accepted by the electron acceptor situated next to
P680.The electron acceptor for PS 2 is phaeophytin.
From this electron acceptor,the electrons of PS 2 are then
transferred down energy levels
through a series of electron carriers.Among the electron carriers are
plastoquinone,cythochrome-f and plastocyanin.
When electron carriers transport electron down the energy levels,energy
is released.This energy is used for photphosphorylation of ADP to ATP.Electrons
from P680 are finally transferred by these electron carriers to P700,the
reaction center of PS 1.
As chlorophyll molecules in PS 2 absorbs light
energy,molecules in PS 1 also absorbs light energy.The energy absorbed by
chlorophyll molecules in PS 1 is channeled to P700,reaction center for PS
1.Photoactivation of P700 occurs,photoactivation of PS 1 occurs.Electrons in
P700 become excited and escape from P700.This loss of electrons from P700 is
replaced by electrons transferred from PS 2.
Electron acceptor located next to PS 1 accepts electrons
escaping from P700.This acceptor is protein Fe-S.From here,these electrons are
then transferred through a series of electron carriers and ultimately to final electron
carrier,NADP+.Each NADP+ accepts two electrons and combine with an hydrogen
ion(from water)to form NADPH.
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