well now continuing on
with our review of the overall
process of
the light dependent reactions we see that ATP is produced
via chemiosmosis and ATP synthase is
responsible for
harnessing the energy of proton flow
through the thylocoidmembrane
in order to drive the synthesis of 
ATP
using ADP and inorganic phosphate and
we've studied this proton flow
so
another way to review this whole process
is to look at the famous z diagram so
called because this looks like Z
on its side so we have photo-system 2
capturing
light energy elevating electrons to a higher energy state
in an excited reaction center passing
those electrons on
plastoquinone and replacing those
electrons from water
and as the electrons are transferred from plastoquinone
through the B6F complex and
then to
plastocyanin we have a proton gradient
formed by  the pumping of hydrogen ions by
the B6F complex
plastocyanin passes those electrons
on to photosystem 1 and
photosystem one has lost electrons
due to absorbing photons of light
transferring that energy to the reaction center
and
having electrons with elevated
energy is being passed on
to feridoxin those electrons being
replaced by
electrons coming in from plastocyanin and ultimately
feridoxin passes electrons on to NADP
to form NADPH and the enzyme that
catalyzes that
oxidation reduction is NADP
reductase so this is the overall Z
diagram
and it's useful to study this and
so you might want to freeze your
movie here and examine this in a
little more detail
and be sure you understand the flow of
electrons here
and the nature by which the two molecules
that are essential for
driving the subsequent light independent
reactions are going to be produced so
NADPH and then ATP through the
not shown here through the chemiosmotic
synthesis of ATP
now what I'm going to do is show you again by
review
a couple movies that I pulled off the web
so this will be further review for you
okay that was rather quick I know
but if you can relate that to what we
read we've reviewed already
you'll be doing really well so lets take a peek at another one
the process of photosynthesis
produces ATP from ADP and PI
by using the energy from light to excite
electrons
that are passed along an electron
transport chain
coupled with the transfer of electrons
is the pumping of hydrogen ions
and the splitting of water molecules
the following complexes are found in the
photosynthesis
electron transport chain
photosystem 2
cytochrome b6f
photosystem 1
ferredoxin NADP reductase
and the complex that makes ATP; ATP
synthase
in addition to the complex's three
mobile carriers are also involved
plastoquinone QB
plasocyanin
and ferredoxin
other key components include photons
chlorophyll molecules
protons
water
molecular oxygen
NADP
and the electrons to form NADPH
and ADP and PI
which combine to form ATP
photosynthesis occurs in  the chloroplasts of plants
and algae the process is also found in
single-cell organisms
such as cyanobacteria that do not have
chloroplasts
like its mitochondrial counterpart the
chloroplast electron transport chain
consists of several protein complexes
and mobile electron carriers
first a photon of light hits a chlorophyll
molecule
surrounding the photosystem 2 complex
this creates resonance energy
that is transferred through neighboring
chlorophyll molecules
when this energy reaches the reaction
center imbedded in photosystem 2
an electron is released
the reaction center chlorophyll contains
electrons
that can be transferred when excited one
photon is needed to excite each of the
electrons in this chlorophyll
once excited  two electrons are transferred
to plastoquinone QB
the first mobile carrier
in addition to the two electrons QB also
picks up two protons from the stroma
the two electrons lost from photosystem
2 are replaced by the splitting of
water molecules
water splitting also releases hydrogen
ions into the lumen
this contributes to a hydrogen ion
gradient similar to the one created by
mitochondrial electron transport
after two water molecules have been
split one molecule of
molecular oxygen is created
plastoquinone QB then transfers the two
electrons
to the cytochrome b6f complex
the two protons it picked up are
released into the lumen
these transfers are coupled with the
pumping of two more hydrogen ions into
the lumen space
by cytochrome b6f
the electrons are next transferred to
plastocyanin
another mobile carrier next the
electrons are transferred from plastocyanin
to the photosystem 1 complex
it is here that photons again energize
each electron
and propel their transfer to ferradoxin
ferradoxin then transfers the electrons
to the ferradoxin NADP reductase
also known as FNR
after two electrons are transferred to
FNR
NADPH is made by adding the two
electrons and a hydrogen ion
to NADP
the gradient created by the electron
transport chain
is utilized by ATP synthase to create ATP
from ADP and PI
this is similar to the way ATP is
synthesized in the mitochondria
ATP, NADPH and molecular oxygen
are the final vital products of photosynthesis
so those were some very nice movies
especially the latter one produced at North Dakota State
now what I'd like to do is go over some experiments
that show the importance
of key features of the photosystems and that's where we'll pick up with next
