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Procaryotic
Cell
The
procaryotic
cell,
is
characterized
by
the
absence
of
the
ER
and
the
cytoplasmic
membrane
is
the
only
unit
membrane
of
the
cell.
However,
this
membrane
may
be
sometimes
infolded
deep
into
the
cytoplasm.
Electron
microscopy'
of
most
procaryotes
reveals
only
two
internal
regions,
the
cytoplasm
and
the
nucleoplasm.
The
cytoplasm
is
granular
in
appearance
and
contains
ribosomes
that
are
smaller
in
size
as
the
compared
to
eucaryotic
risbsomes.
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The
nucleoplasm
is
fibrillar
and
contains
DNA
Expert
in
mycoplasmas,
other
procaryotes
contain
a
defined,
rigid
cell
wall.
No
membranous
structures
similar
to
the
mitochondria
or
chloroplasts
are
seen
in
the
procaryotes.
The
cytoplasmic
membrane
is
the
site
of
the
respiratory
electron
transport
in
procaryotes.
In
photosynthetic
bacteria,
the
photosynthetic
apparatus
is
located
in
a
series
of
membranous,
flattened
structures
similar
to
the
thylakoids
and
these
structures
are
not
organized
into
chloroplasts
but
are
dispersed
in
the
cytoplasm.
The
cytoplasmic
membrane
contains
specific
sites
for
DNA
attachment
and
also
has
a
major
role
in
cell
division.
The
cell
membrane,
unlike
in
the
eucaryotic
cell
does
not
generally
contain
sterols
and
polyunsaturated
fatty
acids.
The
fatty
acids
present
are
generally
of
the
saturated
type.
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The
genetic
material
in
the
procaryotic
cells
is
located
in
the ‘nucleoplasm’ which
lacks
a
defined
nuclear
membrane.
It
consists
of
double
helical
DNA
without
any
associated
basic
proteins.
The
size
of
the
DNA
in
procaryotic
protists
is
much
smal1er
than
that
in
eucaryotes.
Procaryotes
also
contain
extra
chromosomal
DNA,
which
can
replicate
autonomously
called
the
plasmids.
These
can
be
lost
from
the
cell
without
impairment
of
cell
viability.
Procaryotic
cells
exist
in
a
haploid
state
and
divide
by
a
process
very
similar
to
mitosis
although
distinct
stages
are
not
recognized.
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