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Bacterial
Photosynthesis -
In
bacterial
photosynthesis,
a
quantum
of
visible
light
is
absorbed
by
a
molecule
of
chlorophyll
a
or
a
molecule
of
a
carotenoid
and
the
energy
is
then
transferred
to
another
chlorophyll
in
a
special
reaction
centre
causing
the
ejection
of
an
electron.
This
electron
is
then
accepted
by
ferrodoxin
and
the
oxidized
chlorophyll
oxidizes
the
terminal
cytochrome
of
the
electron
transport
system
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The
resulting
charged
system,
with
a
large
potential
difference
between
its
termini
is
used
to
produce
ATP
(photophosphorylation)
and
the
reducing
power
in
the
form
of
TPNH,
which
are
both
used
in
the
reduction
of
CO2
.
The
amount
of
ATP
and
TPNH
formed
in
this
system
varies
depending
on
the
photophosphorylation
system.
In
cyclic
photophosphorylation,
the
electrons
are
transferred
from
the
reduced
ferredoxin
to
oxidized
cytochrome
through
a
chain
of
quinones
and
cytochromes
in
a
close
circle
which
leads
to
the
conversion
of
a
part
of
the
absorbed
light
into
energy.
In
the "noncyclic
photophosphorylation",
the
electrons
at
the
reducing
end
of
the
chain
are
used
to
reduce
NADP
and
to
complete
the
electron
transport,
electrons
must
be
supplied
from
an
another
source.
In
photosynthetic
bacteria,
these
electrons
are
derived
by
the
oxidation
of
a
substrate
other
than
water
and
therefore
no
oxygen
is
released.
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Photosynthesizing
bacteria
are
generally
obligate
anaerobes.
Bacterial
photosynthesis
is
also
more
primitive
in
that
the
photosynthetic
apparatus
is
not
found
in
chloroplasts
but
in
particles
attached
to
the
extensions
of
the
plasma
membrane.
With
the
use
of
energy
and
the
reducing
power
supplied
by
photosynthesis
or
chemosynthesis,
the
autotrophic
bacteria
reduce
CO2
to
derive
their
(carbon
requirement.
Although
this
process
is
fundamentally
biosynthetic,
it
is
ultimately
linked
to
autotrophic
energy
metabolism
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