PHOTOSYNTHESIS - Video Lecture Video Lecture - Class 11

the process of photosynthesis produces
ATP from ADP and P I 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 ii cytochrome b6f
photosystem one ferredoxin NADP
reductase and the complex that makes ATP
ATP synthase in addition to the
complexes three mobile carriers are also
involve plastoquinone QB
plastocyanin
and ferredoxin
other key components include photons
chlorophyll molecules
protons
water
molecular oxygen
NADP and the electrons to form NADPH and
ADP and P I
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 embedded 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
two 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
plasticine 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 ferredoxin
ferredoxin then transfers the electrons
to the ferredoxin 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 P I
this is similar to the way ATP is
synthesized in the mitochondria ATP
NADPH and molecular oxygen are the final
vital products of photosynthesis
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