The
flagellar
apparatus
is
composed
of
three
distinct
parts
namely
the
filament,
the
hook
and
the
basal
granule.
The
outermost
structure
is
the
filament
which
is
a
fibre
composed
of
a
protein
known
as
flagellin
(subunit
molecular
weight
20,000)
and
this
is
attached
to
the
basal
granule
with
the
aid
of
the
hook.
The
hook
and
the
basal
granules
contain
proteins
which
are
antigenically
distinct
from
the
flagellin.
The
basal
body
consists
of
a
small
central
rod
inserted
in
to
a
system
of
rings
and
the
unit
operates
basically
as
a
simple
motor.
Growth
of
the
flagella
occurs
by
the
addition
of
the
flagellin
subunits
at
the
distal
end
after
being
carried
through
from
the
cytoplasm,
apparently
through
the
hollow
core
of
the
flagellum.
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